The mean and variance of a variable

Abstract

Much of regression analysis, indeed much of statistical analysis in general, involves the related concepts of mean and variance. The mean and the variance are known as “descriptive“ statistics. They are summary measures that describe the basic characteristics of a distribution of numbers. The mean is a measure of central tendency. As such, it conveys information about the “center“ or “midpoint“ of a distribution of numbers. The variance is a measure of dispersion. It conveys information about the “spread“ or “variability“ of the numbers in a distribution around the mean. Together, the mean and the variance tell us a great deal about the distribution of any variable.