The Feasibility Analysis of Mathematics Textbook Material based on Bell's Criteria

The purpose of this study is to determine the feasibility of Mathematics textbook material for Grade VII 1st semester on 2017 Revised Edition based on Bell's criteria. So that if there is an error, it can be fixed. Then, this type of research is descriptive research. In the descriptive analysis, there is no need to find or explain its relationships and test hypotheses. The approach used is qualitative. Moreover, this study uses a qualitative approach because the data collected are described in sentences. This study will be obtained from two sources, namely the main source of the Mathematics Textbook Grade VII of 2013 curriculum and peer-discussion support sources. The method used in this research is the documentation method. The documentation data used in this research is the textbook itself. However, the data obtained by using the Analysis Instrument Result shows that the suitability of the mathematics textbook material of Grade VII with the material based on Bell's criteria for the numbers and algebra chapters includes a good category. Meanwhile, the sets and equations and linear inequalities of one variable chapter belong to be an excellent category. The average suitability of the mathematics material from each chapter in the textbook toward Bell's criteria is 83.75% and is supported by the validity data results through forms and peer discussions. As a result, the feasibility of the mathematics textbook material for grade VII of the 2017 revised edition based on Bell's criteria is very good.


INTRODUCTION
Learning experiences are the main activities in the educational process. National education in Indonesia is defined as a conscious and planned effort to create a learning atmosphere and learning process so that students actively develop their potential to achieve certain goals, which are characterized by the involvement of a number of interrelated components. Moreover, the studying and learning process elements are Hipotenusa Journal, 3 (1), June 2021 Mahendra Wisnu Wardana, Leetahannee Kadah 2 called learning tools that consist of a lesson plan, learning tools/instruments that include methods, media and learning resources, and evaluation tools, both tests and non-tests (Hanafy, 2014).
Learning resources are needed to support the teaching and learning process in schools, from elementary to higher education. Then, one of the most widely used learning resources in schools is textbooks. Textbooks help teachers in delivering material, while for students, textbooks support them in mastering the material and could be used for independent learning (auto-pilot learner).  The use of textbooks is inseparable from the selection process seen from the objectives, learning orientation, and student development to make it easier for students to master teaching material in the textbooks. Therefore, textbooks are books whose presence is needed by students in the class' supporting the learning process and as material for independent learning outside the classroom.
Before being used by the academic units, the textbooks have passed the textbook's feasibility test of the various components. In presenting materials, books must contain perfect elements because they will be used as sources of information for teachers and students. Pradita and Fitriani (2018: 282) state that the world of education in Indonesia has always paid close attention to the feasibility of textbooks in every discipline since a long time ago. There are various rules and criteria for determining the feasibility of composing and presenting a book. The government has made efforts to provide quality textbooks. As a result, the government there is the formation of the National Education Standards Agency (BSNP), one of the duties is to assess the feasibility of textbooks. In the Regulation of the Minister of National Education of the Republic of Indonesia (Permendiknas RI) No. 2 of 2008 concerning the book of Article 4, Paragraph 1 states that "Textbooks at the primary and secondary education levels are assessed for their feasibility first by the National Education Standards Agency (BSNP) before being used by educators and/or students as a learning resource." So, if each academic unit wants to use a textbook to help the process of teaching and learning activities, it is required to have a BSNP.
The National Education Standards Agency (BSNP) has its own criteria for textbooks used in the learning process. (Muljono, 2007) explains the criteria for a good textbook, namely first, at least it refers to students' achieved goal, in this case, is the competency standards (SK and KD), secondly contains information, messages, and knowledge which are written and able to be communicated to the readers (especially teachers and students) logically, easily accepted based on the readers' cognitive development level. Then third, it contains attractive and interactive presented concepts and interactive manner which can encourage critical, creative, innovative and deep thinking processes, as well as metacognition and self-evaluation, the fourth is based on its appearances, it would present an attractive cover and describes the characteristics of textbooks, 'read and use' eligibility and books' appearance quality.
When compared BSNP criteria with Bell's criteria, both have similarities with the material; SK and KD, material suitability, and material accuracy. Bell (Melissa, 2015) said that mathematics material in the textbooks must be correct and must be adjusted to the learning objectives and the type of students who will take part in the learning. The method of delivering the material is also an essential thing in book evaluation. The importance of evaluating mathematics textbooks is to determine the suitability of these books with the intellectual development's level and the students' ability level.
The government in Indonesia is currently implementing a 2013 curriculum education system. The textbooks used also follow curriculum changes, including grade VII semester 1 mathematics textbooks revised edition 2017. However, not all academic units in Indonesia use this textbook. Each education unit should have used the latest edition of the book because it supports the teaching and learning process in schools and is adjusted to the current curriculum.
Based on the description above, to prove the feasibility of the contents in the 2013 revised edition 2017 curriculum mathematics book for grade VII semester 1, an analysis of the book was carried out using Bell's criteria. The reason for taking the book was because the 2013 revised edition 2017 curriculum mathematics book for grade VII semester 1 was a book copyrighted by the Ministry of Education and Culture of the Republic of Indonesia in 2017, which was used as a learning resource. Since most schools in Indonesia use these books, it is necessary to guarantee their quality. This research was conducted to determine the feasibility of a Mathematics textbook based on Bell's Criteria.

METHOD
This type of research used for this research is descriptive research. (Hardani, 2020) Descriptive analysis is directed to provide symptoms, facts, or events systematically and accurately regarding the characteristics of a particular population or area. There tends to be no need to find or explain mutual relationships and test hypotheses in descriptive research.
The approach used by researchers for this research is qualitative. According to (Sugiyono, 2018) qualitative can be used to examine the conditions of natural objects, where the researcher is a crucial instrument, data analysis is inductive/qualitative. This study uses a qualitative approach because the data collected will be presented in words arranged in a sentence.
This study analyzes the feasibility of the mathematics textbook material for grade VII of the 2017 revised edition based on Bell's criteria. The description in this study is carried out by providing an overview and an overall assessment of the textbook based on Bell's criteria relating to mathematical material. and supporting sources from peer discussion. Then, the method used in this research is the documentation method. According to (Hardani, 2020), the documentation method comes from the word document, which means written goods. Meanwhile (Rasimin, 2019) defines a process of collecting data that comes from non-human sources. So, the documentation method means how to collect data by recording the existing data.
Documents can be in writings, pictures, or monumental works of a person. Documents included in the report include diaries, life histories, stories, biographies, regulations, policies. Though, documentation data used in this study is the 2013 Curriculum Mathematics textbook of 2017 Revision Edition Grade VII 1st Semester. Data obtained using the Book Conformity Analysis Sheet instrument based on Bell's criteria are in the form of a checklist. This check-list is filled by placing a checkmark (√) in one of the "yes" or "no" columns based on the analysis result of the book's suitability to Bell's criteria.
Moreover, (Hardani, 2020) argues that data analysis is the process of systematically searching and compiling data obtained from interviews, field notes, and documentation by organizing data into categories, describing them into units, synthesizing, arranging them into patterns. , choosing which ones are important and what will be studied, and making conclusions so that they are easily understood by oneself and others. The data analysis model in this study uses the data analysis model of Miles and Huberman. In (Hardani, 2020) the data analysis of Miles and Huberman's model is divided into three lines, (1) data reduction, (2) data presentation and (3) drawing conclusions. Data reduction in this study focuses on the suitability of the 2013 curriculum of the 2017 revised edition of mathematics textbook material for grade VII 1st semester based on Bell's Criteria.
Furthermore, the data presented will be presented in the narrative text from a brief description and results in analysis table of the suitability of the material in the textbook and then conclusions drawn from the results. The data analyzed in this study are book suitability data which come from research's documentation method. The book suitability data analysis technique can be described as follows.
In this study, the feasibility of the mathematics textbook material for grade VII 1st  To check the validity of the data, an examination technique is needed. There are four criteria used, namely the degree of trust, transferability, dependability, and certainty.
(1) The trust degree has the function to carry out an inquiry in such a way so that the confidence's level of the inventor can be achieved and shows the confidence's level of one finding by the researcher's prove (Moleong, 2017).
(2) Transferability means that an invention can be used or applied to all contexts. To carry out this diversion, the researcher looks for and collects the empirical events of the similarity in context (Moleong, 2017). (3) Dependency is a substitute for the term reliability, which is indicated by conducting a replication of the study. Reliability happens when a study is repeated in the same condition and gets the same results (Moleong, 2017). (4) Certainty, the criterion of certainty, comes from the concept of objectivity according to nonqualitative terms, which is determined in terms of the agreement among subjects. The  (Moleong, 2017).
Thus, four criteria of data validity, each of them have an examining technique.
The examining techniques, according to (Moleong, 2017) can be seen in table 2. In this study, the researcher uses the persistence technique of observation and peer-review. (Moleong, 2017) Observational persistence means looking for consistent interpretations in various related to a constant or tentative analysis process. So the continuation of observations in this study aims to increase accuracy and detail in analyzing the feasibility of the mathematics textbook material for grade VII 1st semester of 2017 revised edition based on Bell's criteria. Furthermore, peer-review is through discussion to strengthen the findings. (Moleong, 2017) suggests that peer-review techniques are carried out by exposing temporary results or the final results obtained by peers-discussion. Moleong (2017) describes that the certainty criterion requires researchers to report the results of their research so that the description is carried out as carefully and accurately as possible, describing the context of the study. So the researchers provide reports carefully to explain the results of the suitability mathematics textbook's analysis While dependence is done by auditing. It completes the overall implementation records from the study results or analysis of the material in the seventh-grade mathematics textbook in the first semester of the 2017 revision. In (Moleong, 2017) auditing is a business concept, especially in the fiscal field which is used to check dependability and certainty. This is both happened toward the process or on the results or the output.
Based on the above background, the problem formulation in this study is how the feasibility of the mathematics textbook material for grade VII 1st semester of 2017 revised edition based on Bell's criteria? The aim of this research is to describe the feasibility of this textbook.
The results of this study are expected to be valid and improve the quality of textbooks to support the development of education in Indonesia to make it even better.
Teachers' practical benefits can provide insight, overview, and be more selective in using textbooks as learning resources for students. The teacher must be more careful in the book's contents, especially the material in the book, provide suggestion, and correct it if there are errors in the textbook before it is delivered to the students. In contrast, for students, it can be used as a source of information about how to choose a good textbook and be more selective in selecting textbooks as a learning resource.
To provide direction and goals to be achieved in this research, it is necessary to emphasize the terms. According to (Mujiati, 2014) analysis can be defined as the decomposition of a complete information system into its parts to identify and evaluate problems, opportunities, obstacles that occur, and the expected needs so that improvements can be proposed. Meanwhile, feasibility, according to the Indonesian Dictionary/ Kamus Besar Bahasa Indonesia (KBBI), means something appropriate and valuable to find out a result. So the feasibility analysis is describing information to find out the products that are precious to do. In this study, the feasibility analysis is used to describe the material for mathematics textbook material for grade VII 1st semester of 2017 revised edition to determine its feasibility before being used for the teaching and learning process.
According to the Indonesian Dictionary (KBBI), criteria are the measurements are the basis for an assessment or determination of one thing. (Lutviana, 2017)  Bell, but this study only takes 1 criterion, namely criteria related to mathematics material. The first criterion contains 21 questions, but these questions are modified based on the curriculum on the analyzed students' book so that there are 20 questions for each chapter.
The analysis explains a complete information system into its parts which aimed to identify and evaluate problems, opportunities, obstacles that occur, and expected needs so that improvements can be proposed (Mujiati, 2014). Based on the description above, it can be concluded that analysis is the activity of describing or sorting out information based on specific criteria to evaluate the problem so that it can be corrected immediately.
Learning resources come from two words, namely source and learning. The source is commonly known by the terms origin, the beginning, and material. Learning is all events or activities that affect students' learning process (Zaman, Application of Active Learning in PAI Learning, 2020). Meanwhile, learning is a process of seeking experience. So learning resources are all materials that facilitate one process of gaining experience (Satrianawati, 2018). Then, (Susilana, 2007) states that learning resources are anything that supports the learning process, including service systems, learning materials, and the environment.
Textbooks contain material descriptions of specific subjects or fields of study, which are arranged systematically and have been selected based on specific objectives, learning orientation, and student development, to be assimilated .
Mudzakir also conveys a similar definition. Textbooks are school books, teaching books, handbooks, or textbooks used in schools or educational institutions and are equipped with materials for training or student's handbooks (Mudzakir, 2003).
Meanwhile, based on the understanding of textbooks according to the experts, it can be concluded that textbooks are lesson-books that have been tested for the feasibility of content from various aspects so that they can be used as a handbook for teachers and students in schools to support and facilitate teaching and learning activities in school.
Quality textbooks are books that can be used in the teaching and learning process.
Textbooks function as teaching materials that are adapted to the current curriculum and following the level of education that students are taking.   Based on the textbook quality standards above, it can be said that textbooks have an important role as a companion to teachers and students in teaching and learning activities, because textbooks can help students to grow their motivation and interest in learning for independent study based on the material listed in the textbook. According to (Hidayat, 2007) the existence of textbooks for teachers in schools is a very determining factor in the success or failure of an educational process in schools.
In choosing textbooks, the teachers must pay attention to the quality of the book from various aspects such as book cover, type of paper used, and book material based on the level of education. Meanwhile, Mathematics comes from Greek from the root word mathema which means knowledge or science or other similar words mathenin which means learning or thinking. (Siagian, 2016) argues that mathematics means knowledge gained by thinking (reasoning). Mathematics has characteristics there are: having abstract objects based on agreement, deductive thinking, having symbols that are empty meaning, paying attention to the overall discussion, being consistent in the system. Then, Mathematical objects are mental which cannot be sensed, seen, touched, or felt. From the explanation above, it can be concluded that mathematics is an abstract and consistent science or an exact science that is obtained by thinking and reasoning.
So a mathematics textbook is a student and teacher handbook that contains mathematics learning material to support the delivery of mathematical knowledge.
Mathematics textbooks are expected to help teachers deliver material and give students motivation to learn mathematics at school and outside of school independently.
Experts defined the meaning of the curriculum as very diverse because of different bases and thought. Even though they are different, they still have similarities, namely the curriculum as a tool to achieve educational goals. The curriculum has a system that consists of various interrelated components and has only one educational goal. According to (Winarso, 2015)  In general, in textbooks there are teacher instructions that are used to assist teachers in delivering material to be accepted by students quickly and in a structured manner. Many secondary schools' textbooks come with teacher editions or teacher guides that contain specific information and sections such as test guides, learning objectives, appendices, and introductory chapters, which are helpful for teachers in planning and teaching.
The 2013 curriculum on Mathematics is different from the previous curriculum.
The previous curriculum directs the learning process to the abstract material, but in the 2013 curriculum starts from observing concrete problems, then to semi-concrete, and finally problem abstraction. In addition, if in the previous curriculum, students were only asked to memorize formulas to solve problems, but in the 2013 curriculum, the formulas are derived by students themselves. The problems on the number of questions have to be assigned by students only with basic formulas and understanding so that students could use not only formulas but also understand their origins.
The approach used in the 2013 curriculum is scientific. The scientific approach is considered as an approach that can develop the activeness and creativity of students because in this approach, there are important components, including observing, questioning, reasoning, trying, and presenting components so that they can support the learning process and its results. Learning outcomes are the final results that have been achieved by a person after carrying out a learning process that the results in these changes as follows: a). Behavior, b Based on the description above, the researcher expects this study to run optimally and in line with the research objectives regarding its feasibility. Then, based on Bell's four criteria, this research will use the first criteria related to mathematical material.
Because the material is crucial in the book, if there is a material error, it will have fatal consequences for teachers and students who use it.
The topics discussed in the textbook must be based on the Permendikbud and adapted to the level or grade. The topics that must be presented in the mathematics textbook for grade VII 1st semester according to   In the algebra chapter, symbols and notations are used, one of which is the use of symbols or variables x and y. In question 6, does the book contain a number of typographical errors and wrong answers that affect understanding the material? The algebra chapter contains several typographical errors and solutions that can influence students in understanding algebraic material.

RESULTS AND DISCUSSION
Question 7, Does the material presented use too many symbols that are not appropriate so that it affects students' understanding? The use of symbols is appropriate and does not affect students' understanding, so it can be said that it fulfills Bell's criteria.
Question 8, Is the basic structure of the mathematical system clearly presented? The basic structure of the mathematical system is clearly presented. One of them is to find the width of a flat area. First, the formula for finding the area of a flat area is presented.
In algebra, there are also mathematical figures. So that it meets Bell's criteria for Question 7, Does the material presented use too many symbols that are not appropriate to affect students' understanding? The use of symbols is appropriate and does not affect students' understanding, so it can be said that it fulfills Bell's criteria.
Question 8, Is the basic structure of the mathematical system clearly presented? The basic structure of the mathematical system is clearly presented. One of them can be seen in the set chapter is in the 13 th question. Based on the results of the discussion, the proof of the theorem is not overly emphasized because the students' abilities seem hard to face the logic of proof. Furthermore, the differences in the algebra chapter contained in questions 14 and 16. Based on the results of the discussion, when looking back 2013 curriculum objectives, students are required to think critically, so solving the problem in question 14 does not affect students' understanding. The last difference is the general logic error, which is explained in the problem-solving problem book using the unit size of rice sacks. But then it is discovered that the unit of mass/kg (weight) of rice is not previously explained. Based on the results of the discussion, rice generally has a mass (on kg), so even though it is not previously explained, it would not affect students' understanding of the problems presented in the book.
Based on the observational data contained in Appendix 5, the analysis and discussion of the suitability of the observations related to the material based on Bell's criteria have been carried out, a recapitulation of the results of the analysis is presented in table 3. Furthermore, there is a difference opinion between the results of the researcher's analysis and peer-review. The first difference is in the number chapter, the previous fraction material has not been conveyed about KPK material. But KPK material has been taught at the previous level, namely in elementary school. To solve a problem such as the question 10's case, students will usually immediately equate the denominator without paying attention to the use of KPK.
The second difference opinion in the 13 th question set chapter, from the teacher's experience of the theorem of proof of a material is not emphasized in details, only briefly conveyed. Because the ability of grade VII students is still difficult in proving the theorem. Looking at the current 2013 curriculum, for the future, the proof of the theorem will be conveyed in more detail because theorem's proof can affect the students' mindset to be more creative. So that the goals of the 2013 curriculum can be achieved.
The third difference of opinion is found in the algebra chapter, for problem solving if it is related to the 2013 curriculum, students are required to think critically. So when looking back at the case of question 14 in the algebra chapter, it does not matter if it is not explained. The goal is that students can solve these problems independently.
However, the fourth difference is still in the algebra chapter, logical errors in the algebra chapter of question 16. The problem that occurs is the use of mass units of rice.
Previously the unit used is the unit of rice sacks, but in the following context it changed to kilograms of rice (mass on kg). In general, the mass unit of rice is kilograms. So students can still solve the presented problems/questions and do not affect student understanding.

CONCLUSION
Based on the results of the discussion and analysis, it could be concluded that the suitability between the material in the Mathematics Student Book for Grade VII 1 st Semester and the material based on Bell's criteria for the numbers and algebra chapters based on table 3 for this chapter is in a good or appropriate category. In the set and linear equations and inequalities chapter, one variable based on table 3 belongs to be the excellent category. The average suitability of the mathematics material from each chapter in the textbook against Bell's criteria is 83.75% and is supported by the results of the validity of the data through forms and discussions with peers. Finally, the appropriateness of the mathematics textbook material grade VII 1 st semester 2017 revised edition based on Bell's criteria are categorized as very good.