ABSTRACT
This chapter focuses on descriptive statistics, such as ratios, rates of change, and distributions as well as means, medians, modes, and standard deviations. Simple descriptive data are often used to paint compelling pictures. Measures of central tendency look at the distribution as a whole and provide a single number that best describes the center of the data. Sometimes using a mean makes it easier to summarize data, especially data from all fifty states. Comparison of means is a better way to summarize and describe the data. For instance, analysts want to compare grade point averages (GPA) of men and women in a Master's of Public Administration program. Measures of dispersion show how far the data are from the mean. By definition, this is used with interval/ratio-level data, including ordinal data that have been changed to be treated as interval-level data. The most commonly used measure of dispersion for interval or ratio data is the standard deviation.
