ABSTRACT
This chapter presents information about three important characteristics of data: the shape of the distribution, measures of central tendency, and measures of variability. All of these descriptive statistics will play important roles as student learn to use statistical tests. Before examining several statistics used to describe data, authors need to mention a few issues regarding the collection and organization of the data. Several statistics are available to quantify the center of a distribution. These statistics are referred to as the measures of central tendency. The mean is probably the most commonly used measure of central tendency, because it is sensitive to the actual value of every score in the distribution. To overcome the instability issue of the range, authors can use the semi-interquartile range as an indicator of the variability of a distribution.
