Evaluation of Trends in Theses on Socio-Scientific Issues: The Case of Turkey

The purpose of the current study is to determine the trends in M.A and Ph.D. theses on socioscientific issues. To this end, thesis studies completed between 2008 and 2018 on socio-scientific issues were analyzed in terms of the year of thesis and publication type, the university where the thesis is done, the purpose of the thesis, research methods and designs, study groups and their size, data collection tools and the socio-scientific issues preferred for investigation. The thesis studies analysed in the current study were reached from the Higher Education Council Thesis Search Centre Database in Turkey. As a result of the current study, it was determined that such thesis studies started in 2008, the great majority of them are master’s theses, the quasi-experimental design, one of the quantative research methods, was frequently used, documents were generally used as the data collection instruments and pre-service teachers were used as the study groups in most of them. Moreover, in these thesis, the effect of instructional applications directed socio-scientific issues on the related variable (mostly argumentation skill/quality/ability and decision-making skills) has been frequently investigated and the most popular socio-scientific issues selected in these theses were found to include global warming, climate change and nuclear energy. In light of the findings of the current study, suggestions were made for future research and applications to be conducted on socioscientific issues.


INTRODUCTION
In the development of a country, the education system and in the development of an education system, scientific research and applications play an important role. The way to obtain objective, valid and reliable information that is necessary for educational decisions is directly related to the quality of research in the field of education (Yalçın, Bilican, Kezer, & Yalçın, 2009). New ideas and discussions are produced through scientific research conducted in different scientific disciplines and the results are shared with other scientists and interested parties (Ozan and Köse, 2014). However, scientific research and applications have a mission beyond providing academic communication. Academic publications produced as a result of scientific research have goals and contributions such as:  Providing a perspective for the existing theories to continue their development and producing new theories,  Strengthening academic communication among scientists and helping them to progress in their academic career,  Disseminating the produced scientific knowledge through the society,  Providing guidance for new scientific research to be conducted (Chang, Chang, & Tseng, 2010;Lin, Lin, Potvind, & Tsai, 2018;Mortimore, 2000;Ültay & Çalık, 2012) According to Ültay and Çalık (2012), scientific publications, especially the ones based on the revision of educational research, have much to offer to teachers, researchers, educational policy makers and curriculum developers. For example, research involving the analysis of the data elicited in the past is important in determining the methods to be used in the field of education (Tekin, Aslan and Yılmaz, 2016). Therefore, as in many sub-disciplines, research in science and technology education affects the science education policies and curriculum development processes of our country.
As in all scientific fields, the results of scientific research in the discipline of science education are valuable as long as they become operational in practice. In fact, for many years, researchers have stated that research results do not generally make sense in science teaching practices (Shymansky and Kyle, 1992) and mentioned the weak effects of their efforts (de Jhong, 2007). Research directed to science education, however, is not only critical in helping teachers improve classroom practices and contributing to their scientific literacy identity, but is also critical in knowing what has been researched in the past and what needs to be discovered in the future (Chang, Chang and Tseng, 2010).
When the studies investigating the trends in science education were examined, it was found that one of such studies was conducted by Tatar and Tatar (2008). Tatar and Tatar (2008) conducted a study on the basis of the key words of 680 articles published in 26 peer-reviewed journals in [2000][2001][2002][2003][2004][2005][2006] and found that subjects in the elementary school science and math curriculums were less investigated than the subjects in the secondary school and university science and math curriculums and the authors of these articles mostly focused on misconception in science education and attitudes in math education. Karamustafaoğlu (2009) examined all the published issues of 12 journals, nine in print and three with internet access, in order to determine basic orientations in science and technology education by subject areas. They identified the most popular research topics in science education for our country as interdisciplinary relations, educational philosophy, computer assisted science and technology teaching, curriculum development, learning activities and attitude towards science and technology. Ergun and Çelik (2011) conducted a study to determine the trends in science education in Turkey in 2008 and classified a total of 114 master's and doctoral theses according to "research area", "methodology of the study" and "sampling of the study". According to the research area, the most researched area was found to be descriptive. This is followed by studies on science curriculum and science literacy. The area where the least research was conducted was found to be environmental education. In terms of research methodology, the most frequently used methods were found to be experimental and survey methods. In none of the studies investigated, meta-analysis was used and phenomenological, action research, document analysis and case study methods were found to be the least preferred ones. Çalık, Ünal, Coştu and Karataş (2008) examined 444 thesis documents completed between 1990 and 2007. They found that there were general trends in the science education research in Turkey: (1) to promote science education between 1990 and 2000, (2) to follow up new perspectives on the basis of international trends. They also stated that studies involving an intervention and descriptive studies were clearly widespread and that environmental education subjects were studied the least. It was also determined that the most frequently used method was the experimental design while action research, phenomenological and meta analysis methods were the least preferred ones.

Investigation of the Studies Conducted on Socio-Scientific Issues
In the last decade, socio-scientific issues that have social, scientific, political, economic and ethical dimensions, that lead to a dilemma and debate in society, that involve open-ended, unstructured, different perspectives and solutions have become the focus of science education (Evren Yapıcıoğlu and Kaptan, 2017;Fang, Hsu and Lin, 2019;Sadler, 2004). Socio-scientific issues, as the name implies, are real life issues. It is a trend that supports individuals to have a say in decisions about scientific applications that they will encounter in real life and contributes to their being trained as conscious and responsible citizens. In this respect, these subjects are gaining greater importance in science education reform documents (for example, Next Generation Science Standards (NGSS), 2013; American Association for the Advancement of Science (AAAS), 1990) and curricula (MoNE, 2013). Since the 2000s, there has been an accelerated increase in research on socio-scientific issues. These studies are reflected in the curricula and teaching practices of many countries. For example, in the National Science Curriculum revised in 2015 in Korea, socio-scientific issues were further emphasized because they were found to be closely related to the acquisition of various core competences and skills (Lee, 2017). In Turkey, socio-scientific issues, for the first time, were conceptually involved in the 2013 science curriculum. Although the importance of socio-scientific issues was emphasized in the curriculum, it can be said that its reflection on classroom practices was still not sufficient.
In the literature of science education, there are studies conducted for the analysis and general evaluation of the studies on socio-scientific issues. For example, Topçu, Muğaloğlu and Güven (2014) examined 11 articles and 13 thesis studies and as a result concluded that the studies on socio-scientific issues in Turkey could be classified under two sub-themes called as the studies in which socioscientific issues are the means and the studies in which socio-scientific issues are the ends. In addition, they found that most of the studies were at the master's level and quantitative and conducted to describe the pre-determined variables. Tekin, Aslan and Yılmaz (2016) examined 122 articles in five journals with high impact factors at international level between 2004 and 2015. The researchers, in contrast to the results reached by Topçu, Muğaloğlu and Güven (2014), found that there were more qualitative studies in the international literature than quantitative studies. In addition, arguments, decision making and informal reasoning were found to be the most studied variables related to socioscientific issues. In the journals examined, half of the preferred samplings were found to be comprised of middle school and high school students, followed by university students. In their study, Genç and Genç (2017) concluded that the articles published in the period between 2000 and 2014 on socioscientific issues in Turkey mostly focused on the themes of knowledge level, attitude and awareness and that in qualitative studies, undergraduate students were preferred more and that the most frequently researched socio-scientific issue was global warming. Lee (2017) analyzed the studies focused on socio-scientific issues by using the thematic content analysis method. It found that researchers in Korea primarily focused on identifying factors that might affect students' informal reasoning processes in socio-scientific issues, secondly on examining decision-making models in socio-scientific issues, and thirdly on teaching practices in socio-scientific issues.

Significance and Purpose of the Study
Today socio-scientific issues are among the subjects frequently faced and debated by people in Turkey and in the world. Chang, Chang and Tseng (2010) stated that socio-scientific issues had attracted more and more attention over the years in studies conducted in the field of science education. In the studies based on the revision and evaluation of the studies on socio-scientific issues, published articles were found to be used as the most popular data sources (Genç and Genç, 2017;Lee, 2017;Tekin, Aslan and Yılmaz, 2016). In determining the trends in a research subject area, theses done in this area can be said to be an important data source. The fact that thesis studies are published in the language of the country in which they are done most of the time may cause limitation in terms of international exchanges. Moreover, most of the thesis studies are not published in international platforms as articles, papers, books etc. This restricts the functionality of thesis studies in practice.
Like other similar studies in the literature, though Genç and Genç (2017) and Topçu et al. (2014) analyzed the studies conducted on socio-scientific issues in Turkey, their studies are limited to the period between 2000 and 2014. Given that socio-scientific issues have been increasingly becoming subjects of research and that these issues just started to be addressed with the 2013 science and technology curriculum, it can be said that it is necessary to analyze the studies conducted on these issues after 2014. In addition, as different from the existing studies, in the current study, the investigation of socio-scientific issues was limited to thesis studies and moreover, the theses were also investigated from different aspects such as their distribution across universities and the data collection tools used so that more detailed information could be obtained. To this end, theses done in Turkey were used as the main data source and more detailed analyses were performed compared to similar studies in the literature.
Undoubtedly, as scientific research is carried out, new scientific applications and technological products will be developed and people will be confronted with different socio-scientific issues. Therefore, the focus of the current study is on socio-scientific issues that are increasingly emphasized in science education reform documents and are included in science curriculums. With the present study, it is believed that contribution will be made to the sharing of scientific publications (theses done in Turkey) produced in a national framework on socio-scientific issues in international academic environments. In addition, the current study can be said to be a guide for researchers who will plan new research on socio-scientific issues. Thus, the purpose of the current study is to determine the trends in thesis studies on socio-scientific issues in Turkey. To this end, answers to research questions (1. What is the distribution of the theses by year? 2. What is the distribution of the theses across universities? 3. Which research methods were used? 4. Which study groups were used? 5. What is the size of preferred study groups? 6. Which data collection tools were preferred? 7. What are the preferred socio-scientific issues? 8. What is the categorical distribution of the theses according to their purposes?) sought.

Research Methodology
In the present study, the general survey model was employed to conduct a detailed evaluation of theses done on socio-scientific issues in Turkey. The survey method is used to identify trends in a research universe (Fowler, 2008) and to make a description by taking the photo of the current situation (Büyüköztürk, Çakmak, Akgün, Karadeniz, & Demirel, 2010). In the general survey model, a survey is conducted in a universe made up of a large number of elements either on the whole universe or a part of it in order to reach a general judgment about the universe (Karasar, 2006). As a result, the stated purpose of the current study made it necessary to use the survey model.

Data Collection Process
In the current study, the Higher Education Council Thesis Search Centre Database official site was used to reach the thesis studies done on socio-scientific issues in Turkey. As a result of the preliminary search, it was determined that the first thesis on socio-scientific issues was published in 2008. For this reason, it was decided to include the theses done in the period between 2008 and 2018 in the current study. In the search, the Turkish key words "sosyobilimsel" and "sosyo-bilimsel" and their English translations (socioscientific and socio-scientific) were used. As a result of this search, a total of 55 thesis studies were reached. From among these theses reached, five of them were excluded as four of them don't have access permission and one of them used a sampling out of Turkey (the thesis search process was terminated on 18.02.2019). As a result, a total of 50 thesis study documents constituted the main data source of the study. The criteria used to select the studies to be included in the current study are as follows,  Had to be conducted in the period between 2008 and 2018,  Sampling must be from Turkey,  The title of the thesis must include the concept of socioscientific or socio-scientific,  The thesis must have an access permission in the National Thesis Search Database.

Data Analysis
The data of the study were analyzed by using the content analysis method. The content analysis method refers to a systematic coding and classification operation used to organize certain concepts around codes and themes in existing qualitative data in order to discover the tendencies, frequencies, relationships and structures of the words and sentences used in a large number texts (Vaismoradi, Turunen, Bondas, 2013;Yıldırım and Şimşek, 2008). The main data source of the current study is master's and doctoral thesis documents. In the current study, the thesis data were analyzed qualitatively and then quantitatively converted into tables and graphs.
The analysis process was carried out in two stages. In the first stage, parameters (year and university in which the study was conducted, type of research, method and design of research, study group and its size and data collection tools) were determined in order to determine some descriptive main characteristics of the theses and then the coding was performed. In the second stage, content analysis directed to the variables examined by the thesis studies and the socio-scientific issues they addressed was carried out. In the current study, first the coding process was carried out and similar codes were brought together to create the themes. By combining similar codes, themes were reached. Frequencies of the repeated codes were entered into Microsoft Excel.

Validity and Reliability Studies
In the current study, the selected theses were analyzed by reading again and again to avoid data loss. The coding process was completed nearly within a two-month period. Each thesis study was analyzed on the basis of the pre-determined parameters. Then, the similar codes emerging was combined and thus themes were created. Moreover, as stated by Bağ and Çalık (2017), a confirmation process was followed starting from the findings of the study and progressing towards the themes, codes and finally the raw data. The findings of the data were explained in an unbiased and detailed manner. The fact that the main data source of the current study is documents also strengthens the objectivity of the data. In order to determine the reliability of the coding process, 10 theses accounting for 20% of the research data in the current study and parameters were coded by two experts specialized in qualitative research methods. The inter-rater agreement was calculated by using the formula proposed by Miles and Huberman (1994) and found to be 0.95 and as this is over 0.70, it can be argued that the coding is highly reliable.

Distribution of the Thesis Studies by Year
In the current study, a total of 50 thesis studies completed in the period between 2008 and 2018 were obtained. Of these 50 theses, 35 are master's theses and 15 are doctoral theses. The distribution of these master's and doctoral theses by year is given in Figure 1.

Figure 1. Distribution of doctoral and master's theses by year
As can be seen in Figure 1, the first thesis written on socio-scientific issues was a doctoral thesis by Topçu (2008)

Distribution of the Thesis Studies across Universities
The distribution of the theses done in the period between 2008 and 2018 on socio-scientific issues across universities in Turkey is given in Figure 2.

Figure 2. Distribution of the doctoral and master's theses across universities
According to the 2017-2018 statistics issued by the Higher Education Council, there are 172 state universities and 72 foundation universities; thus, a total of 244 universities in Turkey. As can be seen in Figure 2, in 23% of the universities (9.4%), thesis studies on socio-scientific issues were done. The highest number of master's theses was completed in Abant İzzet Baysal University located in the Black Sea Region and Marmara University located in the Marmara Region and the highest number of doctoral theses was completed in Middle East Technical University located in the Central Anatolia Region.

Distribution of the Thesis Studies according to their Research Methods and Designs
The distribution of the themes, sub-themes and codes related to research methods preferred in the theses on socio-scientific issues is given in Table 1.  As can be seen in Table 1, in the thesis studies conducted on socio-scientific issues in Turkey, the researchers more tended to use quantitative research methods (f = 19). The most preferred quantitative research method is the quasi-experimental pretest-posttest control group design (f = 7). The second most commonly preferred research methods are qualitative research methods (f = 14), followed by the mixed research methods (f = 12). The least preferred research methods are the action research and design-based research approaches. In addition to this, the research design was not specified in 20 thesis studies. In many of the studies in which the research design was not specified, the mixed method was used (f = 7).

Distribution of the Thesis according to Study Group and its Size
The findings related to the distribution of the thesis studies conducted on socio-scientific issues in the period between 2008 and 2018 according to study group are presented in Table 2. It was determined that the study groups preferred in the thesis studies conducted on socio-scientific issues could be classified into three themes (students, teachers and others). *Since more than one study group were included in some theses, the total number of the study group types is different from the total number of theses (50).
As can be seen in Table 2, the most preferred study group is pre-service science teachers (f = 17). The other pre-service teachers (biology, pre-school and social studies) were preferred as the study groups in few of the thesis studies. The second most preferred study group after pre-service science teachers is middle school students. However, elementary and high school students were preferred in a limited number of the thesis studies. The least preferred study group is teachers. Only five of the 50 theses used teachers as the study group. The findings related to the size of the study groups of the thesis studies conducted on socio-scientific issues in the period between 2008 and 2018 are presented in Figure 4. As can be seen in Figure 4, in the thesis studies conducted on socio-scientific issues, the most preferred number of participants is in the range of 11-30. On the other hand, study groups consisted of 0-10 participants were preferred very little in the thesis studies conducted on socio-scientific issues in Turkey.

Categorical Analysis of the Thesis Studies according to the Data Collection Tools Used
Findings related to the data collection tools used in the thesis studies conducted on socioscientific issues in the period between 2008 and 2018 are given in Table 3.

Table 3. Data collection tools used in the thesis studies on socio-scientific issues
Theme Codes ( As can be seen in Table 3, the data collection tools used in the thesis studies conducted on socio-scientific issues were collected under six themes. These are documents, interviews, observations, scales, skill tests and subject-area tests. The most frequently preferred data collection tool was found to be documents, one of the qualitative data collection tools, followed by interviews. The least preferred data collection tool was found to be observations.

Issue Addressed
Findings related to the socio-scientific issue selected to be investigated in the theses done in the period between 2008 and 2018 on socio-scientific issues are given in Table 4.

Table 4. Samples to socio-scientific issues addressed in the theses
Theme Code ( Alternative agriculture suggestions (f:1), destruction of bees in colonies and use of pesticides in agriculture (f:1) 2

TOTAL 100
As can be seen in Table 4, the researchers used social-scientific issues that can be collected under 10 different themes including genetics studies and genetically modified products, energy, human and environment relations, local socio-scientific issues, eating, health, waste control, agriculture, use of animals for experiments and fun and others in their theses. The most frequently preferred socio-scientific issues were found to be gathered under the themes of "genetics studies and genetically modified products" and "energy". When the issues collected under these themes were examined, it was found that global warming and climate change (f=8), nuclear energy (f=7), hydroelectric plants (f=6), genetic duplication/cloning (f=5), organ donation and transplantation (f=4) are the most popular issues addressed in the theses. On the other hand, agriculture, waste control and recycling, use of animals for experiments and fun were found to be the least preferred socio-scientific issues by the researchers.

Categorical Analysis of the Purposes of the Thesis Studies
When the purposes of the thesis studies conducted on socio-scientific issues were categorically analysed, a total of four different themes were obtained. These themes are named as "Determining the effect of socio-scientific issues instructed through different instructional methods/activities on certain variables", "Discovering the states of different study groups depending on different variables in relation to socio-scientific issues", "Determining the relationships between different variables related to socio-scientific issues", "Development and evaluation of an instructional module directed to socio-scientific issues". It is seen that in the great majority of the thesis studies conducted on socio-scientific issues in Turkey, there is some kind of intervention and the effect of this intervention on different variables has been investigated. In these thesis studies collected under the theme "Determination of the effect of socio-scientific issues instructed through different instructional methods/activities on different variables", the effect on a total of 23 different variables was found to have been examined. The codes (variables) found for the Theme 1 are given in Table 5. The most frequently investigated subject is the effect of socio-scientific issues instructed through different instructional methods/activities on argumentation skills (f =7), decision-making skills/tendencies (f = 5), academic achievement (f = 4), informal thinking/reflective judgement (f = 3), scientific thinking skills (f = 3).

Table 5. Determination of the effect of socio-scientific issues instructed through different instructional methods/activities on different variables
Another theme obtained as a result of the categorical analysis of the purposes of theses is "Discovering the states of different study groups depending on different variables in relation to socioscientific issues". Codes and frequency distributions found in relation to this theme are presented in Table 6. As can be seen in Table 6, in the theses aiming to discover the states of different study groups depending on different variables in relation to socio-scientific issues, the researchers most preferred to discover opinions/perceptions/approaches regarding socio-scientific issues (f = 8), followed by argumentation quality/skill/ability (f = 6), critical thinking abilities/ways of analysis/informal thinking skills (f= 3), self-efficacy beliefs/levels (f = 3), epistemological beliefs (f = 3), attitude towards socioscientific issues (f = 3).
Another theme obtained as a result of the categorical analysis of the purposes of theses is "Determining the relationships between different variables related to socio-scientific issues". A total of 6 codes were obtained in this theme. Codes and frequency distributions found in relation to this theme are presented in Table 7.

Table 7. Relationships between different variables related to socio-scientific issues
Codes f Content knowledge * argumentation quality 2 Informal reasoning * epistemological belief * metacognitive awareness 1 Self-efficacy belief * epistemological belief 1 Epistemological belief * ways of instruction in socio-scientific issues 1 Science learning skill * science literacy * attitude towards socio-scientific issues 1 Reasoning * conception of nature of science 1 TOTAL 7 As can be seen in Table 7, the number of the theses investigating the relationships between different variables related to socio-scientific issues was found to be limited. The most frequently investigated relationship is the relationship between content knowledge and argumentation quality. The epistemological belief is the variable whose relationship with different variables was investigated the most.
Another theme obtained as a result of the categorical analysis of the purposes of theses is "Development and evaluation of an instructional module directed to socio-scientific issues". Codes and frequency distributions found in relation to this theme are presented in Table 8.

Table 8. Development and evaluation of an instructional module directed to socio-scientific issues
Codes f Development of content knowledge * argumentation quality 2 Development of argumentation and attitude towards human rights 1 Development of a unit 1 TOTAL 4 As can be seen, a limited number of researchers have been interested in the development and evaluation of an instructional module directed to socio-scientific issues in Turkey. These researchers mostly focused on the development of content knowledge * argumentation quality.

CONCLUSION AND DISCUSSION
The purpose of the current study was to determine the trends in the thesis studies conducted on socio-scientific issues in Turkey. To this end, thesis studies completed between 2008 and 2018 on socio-scientific issues were analyzed in terms of the year of thesis study and publication type, the university where the thesis is done, the purpose of the thesis, research methods and designs, study groups and their size, data collection tools and the socio-scientific issues preferred for investigation. One of the findings obtained from these analyses is that the first thesis study conducted on socioscientific issues is a doctoral thesis by Topçu (2008). Moreover, the findings of the current study have revealed that a significant increase was observed in the number of master's theses as of 2009 and in the number of doctoral theses as of 2013. These findings concur with the findings of Topçu et al. (2014) and Tekin, Aslan and Yılmaz (2016) arguing that the number of the studies on socio-scientific issues gradually increased over time. This might be because socio-scientific issues have gained greater importance both in the world and in Turkey. The rapid developments in the scientific and technological fields and the increasing number of controversial issues brought about by these developments may have attracted more attention to socio-scientific issues and may have made it necessary to investigate these issues. Another reason can be the high increase seen in the number of master's and doctoral theses done on science and technology subjects since 2006 (72%, 71%, respectively) (Doğru et al., 2012). Doğru et al. (2012) associated this increase with the emergence of new research areas due to changes in science curricula since 2005 and rapid scientific and technological developments. Therefore, the increase in the studies conducted in the field of science education in general may have supported the increase in the studies on socio-scientific issues in particular. The increase seen in the number of doctoral theses on socio-scientific issues in Turkey as of 2013 can be attributed to the inclusion of these issues in the formal education curriculum prepared by the Ministry of National Education. It is possible that researchers and educators might have gained awareness of these new subjects that were incorporated into the curriculum and might have wanted to explore the effects of their inclusion of these issues in the curriculum.
Another finding obtained in the current study is that in only 23 of a total of 244 universities in Turkey (9.4%), thesis studies were conducted on socio-scientific issues. According to the findings of the current study, the highest number of master's theses was completed in Abant İzzet Baysal University located in the Black Sea Region and Marmara University located in the Marmara Region and the highest number of doctoral theses was completed in Orta Doğu Teknik University located in the Central Anatolia Region. This finding is parallel to the finding of Değirmenci and Doğru (2017) stating that socio-scientific issues have been most intensely studied in the Black Sea Region and Central Anatolian Region. One of the reasons for this situation can be attributed to the presence of researchers / academicians who are investigating socio-scientific issues in these universities. The panels organized by Marmara University and Orta Doğu Teknik University with the title of Socio-Scientific Issues in Science Education in 2012 can be considered as an indicator of the importance given to socio-scientific issues in these universities.
In the current study, it was determined that the researchers more tended to use quantitative research methods (f = 19) in the thesis studies conducted on socio-scientific issues. This finding concurs with Genç and Genç (2017), Değirmenci and Doğru (2017) and Topçu et al. (2014) demonstrating that quantitative research methods were preferred more in articles and theses written on socio-scientific issues in Turkey. In fact, it can be said that more use of quantitative methods does not only apply to the analysis of socio-scientific issues because in their studies, Çalık et al. (2008), Doğru et al. (2012), Kula Wassink and Sadi (2016) and Varışoğl and Göktaş (2013) found that experimental and survey designs were used the most in science education studies. It can therefore be stated that researchers working in science education prefer quantitative methods. Çalık et al. (2008) brought a different interpretation to the more widespread use of qualitative research in Turkey. They argued that the majority of the researchers researching science education in Turkey had been studying pure science at first and then they got directed to science education; thus, they could not get rid of their past habits. This argument proposed by Çalık et al. (2008) can be viewed as the reason for the findings of the current study. In addition, the fact that qualitative research requires the investigation of events as they are and more in-depth analyzes, whereas in quantitative research, data can be collected more easily and in a shorter time span through data collection tools such as questionnaires and tests, and data can be analyzed quickly with statistical programs may have directed researchers to quantitative studies. Another finding obtained in the current study is that the research method and / or design was not specified in 20 thesis studies and that the majority of these studies are mixed method studies. This finding may be explained by the lack of information about research methods and designs or the lack of care in writing scientific publications.
The results of the current study showed that the least preferred research methods are action research and design-based research approaches. This finding is in compliance with the study carried out by Çalışkan and Serçe (2018) reporting that only in 80 of 3087 articles published in journals with a Turkish address in ULAKBİM and SSCI databases used the action research method, revealing that action research is much less preferred in Turkey. Similarly, Ergun and Çelik (2011) revealed that action research is one of the least preferred methods in science education research, which supports the findings of the current study. Action research, which is used to develop and implement educational practices in a better way (Calhoun, 2002), may require the generation of a new idea of implementation and the development of different perspectives in this regard. The implementation of the proposed innovation in the process and its evaluation with multiple data collection tools at different intervals (Yıldırım & Şimşek, 2008) may make the process long-term and difficult to control. This may have led the researchers to conduct quantitative research in which they could more easily reach the conclusion. The reason why design-based research is less preferred in the investigation of socioscientific issues might be associated with its being relatively new to Turkey. In fact, the first thesis focusing on the implementation of design-based instructions was published in Turkey in 2014 (https://tez.yok.gov.tr/UlusalTezMerkezi/tezSorguSonucYeni.jsp).
The findings of the current research revealed that the most preferred study group in the theses on socio-scientific issues was pre-service science teachers, followed by middle school students. This finding is consistent with Kula Wassink and Sadi (2016) finding that in the articles published in the four basic educational sciences journals in Turkey in the period between 2005 and 2014, the most used study group was pre-service teachers, followed by middle school students. In addition, these findings are consistent with the results of Tekin et al. (2016), which revealed that one of the most preferred study groups in studies conducted on socio-scientific issues in international journals is middle school students. Genç and Genç (2017) determined that in the articles published between the years 2000 and 2014 on socio-scientific issues in Turkey, the most studied study groups were comprised of undergraduate students. Given that Genç and Genç (2017) did not divide the study groups into disciplines and that the pre-service science teachers are also undergraduate students, it can be stated that the results of their study support the results of the current study. Similarly, the results of the study conducted by Topçu et al. (2014) revealing that most of the study groups in the studies carried out on socio-scientific issues between 2002 and 2012 in Turkey were consisted of pre-service teachers are consistent with the results of the current study. This might be partially because of the fact that pre-service science teachers are easily accessible. Another reason may be that, as socio-scientific issues entered the Ministry of National Education science curriculum in 2013, researchers working in the field of science might have attached greater importance to the development of pre-service science teachers on socio-scientific issues and determination of their related competences. In addition, selection of middle school students to be included in study groups of the studies on socio-scientific issues might be the desire to evaluate the functionality and outcomes of these issues newly entering the science curriculum. Moreover, Kula Wassink and Sadi (2016) noted that most of the authors of the articles published in four educational sciences journals between 2005 and 2014 are researchers from the field of elementary school science teaching. Therefore, it can be stated that it is not surprising that the researchers working in the field of science teaching choose pre-service science teachers and middle school students as their samples. Another finding of the current study is that teachers are the least studied sample group in the investigation of socio-scientific issues. Parallel to this finding of the current study, Doğru et al. (2012) and Genç and Genç (2017) have also revealed that one of the least studied groups in Turkey is teachers. One of the reasons for this may be attributed to the fact that teachers do not volunteer to participate in such studies due to different reasons (such as concerns about national exams and keeping up with the curriculum). Moreover, as pre-service teachers are more easily accessible than teachers and these two groups have similar characteristics, pre-service teachers might have been preferred more than teachers.
Another finding of the current study is that in the thesis studies conducted on socio-scientific issues, the most preferred sampling size for these studies was between 11 and 30 participants and the sampling size including participants ranging from 0 to 10 was much less preferred. In the current study, it has also been shown that quantitative research is preferred more than qualitative research. Thus, given that it is possible to conduct a qualitative study with the participation of 0-10 people, it can be said that the research method preferred in the study seems to have affected the sampling size.
Another finding of the current study is that the most frequently used data collection tool in the thesis studies conducted on socio-scientific issues is documents, a qualitative data collection tool (open-ended questions, worksheets, assessment forms, written argumentation activities, reports, researcher notes), followed by interviews and scales. This finding concurs with the study of Varışoğlu and Göktaş (2013) reporting that one of the data collection tools used the most in educational studies in Turkey is documents. The fact that documents are suitable for collective evaluations and many techniques may be one of the reasons why they are more preferred (Varışoğlu and Göktaş, 2013).
In fact, open-ended questions also considered to be documents are one of the most preferred measurement tools in education (Güler, 2014). In addition, students who are dealing with socioscientific issues are expected to be able to put forward their own stance on the issue, make benefit and risk analyzes, and defend their stance with appropriate and sufficient evidence and reasoning (Author, 2016). Therefore, the use of open-ended questions, written forms and worksheets that allow students to express their thoughts may be a requirement of the nature of socio-scientific issues. Another finding obtained in the current study is that in the thesis studies conducted on socio-scientific issues in Turkey, the least preferred data collection tool is observations. This finding of the current study is in compliance with the studies by Kula-Wassinki and Sadi (2016) and Doğru et al. (2012) stating that the least preferred data collection tools in theses and articles in Turkey is observations. This might be because researchers in Turkey generally tend to prefer quantitative research methods because observation is defined as a data collection tool mostly used in qualitative research (Yıldırım, 1999).
Another finding of the current study is that the most preferred socio-scientific issues to be studied in the thesis studies conducted in Turkey include global warming and climate change, nuclear energy, hydroelectric, genetic duplication / cloning, organ donation and transplantation. This finding is similar to the findings reported by Genç and Genç (2017) analyzing the articles written on socioscientific issues between 2000 and 2014 and stating that the most studied issue is global warming and by Değirmenci and Doğru (2017) stating that one of the most studied issues between 2011 and 2015 is nuclear energy. Moreover, this finding is also supported by Genç and Genç (2017) as they found that after global warming, nuclear energy and cloning are the most studied subjects. This finding can be explained by the fact that initially more emphasis was put on global socio-scientific issues in Turkey; thus, more research was focused on the investigation of global warming and climate change affecting the whole world. As the establishment of nuclear power plants is a relatively new development in Turkey and the establishment of these plants is still continuing, the issue of nuclear energy might have turned out to be a popular subject of research. Similarly, news about the plans for the establishment of new hydroelectric plants in the media and public reaction against these new attempts might have fostered researchers' desire to investigate these issues. The use of animals in tests and for fun, agriculture, waste control and recycling were found to be less preferred socio-scientific issues and this might be because these issues have not been much discussed in media in Turkey.
Another finding in the current study is that the highest number of thesis studies analyzed focused on the investigation of the effect of socio-scientific issues on argumentation skills and decision-making skills / tendencies. This finding concurs with the study by Tekin et al. (2016) stating that socio-scientific issues were studied most together with argumentation and decision-making skills in the articles published in five journals having high impact factors. This finding may be related to the necessity of using argumentation and decision-making processes while dealing with socio-scientific issues due to their nature because socio-scientific issues are controversial issues and they do not have definite solutions. Therefore, socio-scientific issues may require individuals to express their own thoughts and to make a decision by defending their thoughts with evidence and reasoning. Therefore, it is natural to investigate the use of argumentation and individuals' decision-making processes while discussing socio-scientific issues in classrooms. On the other hand, the change in the perspective of science education over time may also be a reason for the finding. Nowadays, science teaching is seen from a perspective going beyond the learning of theories and laws or scientific knowledge. Recent approaches in educational research give importance to discursive practices in science learning and emphasize that argumentation; as one of these practices, plays a central role in the development of theories and explanations in science education (Erduran, Osborne and Simon, 2005). Therefore, argumentation has become one of the most emphasized issues in science education for the last 15 years (Tekin et al., 2016). Thus, the finding of the current study showing that socio-scientific issues are mostly studied together with argumentation may be the result of using socio-scientific issues as a suitable content for argumentation.
Another finding of the current study is that in the studies in which correlational analyses were conducted in relation to socio-scientific issues, the correlation most investigated was the one between content knowledge and argumentation quality. The reasons why argumentation is a preferred variable in socio-scientific issues are discussed above. On the other hand, the selection of content knowledge for investigation may be linked to the objectives of science education because although the perspective of science education has changed over time, it is stated that science literate individuals should understand basic science concepts in order to understand the world we live in (Halpern, 2000). Therefore, the objectives of science education can be shown as a reason for examining content knowledge in science education research. The results reported by Topçu et al. (2014) and Genç and Genç (2017) indicating that level of knowledge is one of the most studied variables in studies conducted on socio-scientific issues in Turkey support this finding of the current study. However, while arguing the finding that the correlation between content knowledge and argumentation is one of the most studied subjects in research on socio-scientific issues, it should be kept in mind that only 2 of the theses done in 2008-2018 investigated this correlation. Therefore, we can state that correlation studies are not very common among the studies investigating socio-scientific issues. The finding of Değirmenci and Doğru (2017) that only one of the articles and theses written on socio-scientific issues in Turkey in the period between 2011 and 2015 is a correlation study supports this finding of the current study.
In the current study, it was also found that a limited number of studies were engaged in the development and evaluation of an instructional module in socio-scientific issues from among the thesis studies investigated. In fact, it was found that only one thesis focused on the development of a unit. This might be because of the fact that quantitative methods are preferred more in studies investigating socio-scientific issues in Turkey yet developing a unit and evaluating its functionality may require the use of qualitative processes. On the other hand, these processes may necessitate the cooperation of science education experts and science teachers in the development stage of the unit and that of measurement and evaluation experts in the evaluation of the unit. Accordingly, the fact that the researchers preferred research methods that can reach the results more easily may be a reason for the relevant finding of the current study.

Suggestions
 It is seen that the studies conducted on socio-scientific issues preferred quantitative research methods more. Given that the preferred research method will affect the content of the subject to be investigated, variables or data collection tools, future research to be conducted by using different research methods (quantitative, mixed, correlational, design-based, action research) is believed to make different and important contributions to the socio-scientific issues literature.
 In the considerable number of thesis studies, the research method and/or design of the research was not specified. For this reason, the variety and number of research methods and designs courses offered to especially master and doctoral students can be increased.
 It was determined that a very limited number of studies were conducted on socioscientific issues with the participation of teachers in Turkey. Considering the importance of teachers in the implementation of instructional activities in the classroom, it can be stated that there is a need for studies to be done on teachers. Thus, the findings to be obtained from such studies will support the development of socio-scientific subject-based instruction and allocation of more time to such instruction in classrooms. Therefore, organization of in-service training seminars and projects to inform teachers on socio-scientific issues may also contribute to attachment of greater importance to these issues in the class.
 It is seen that socio-scientific issues have been studied in a very few universities in Turkey. More widespread exploration of these issues can be supported through projects to be realized in cooperation with universities both at national and international level.
 It was found that a considerably small number of studies were conducted to develop socio-scientific issues-based units in Turkey. Research oriented to developing units is believed to serve as an example for educators in terms of including socio-scientific issues in classrooms not only as content but also as a teaching model (socio-scientific issue based teaching).
 Issues such as pesticide use in agriculture and alternative agriculture are the least studied socio-scientific issues in Turkey. Investigation of such issues in an agriculture country like Turkey is of great importance for people to produce their agricultural products more consciously.