Chapter 3. Descriptive statistics for quantitative variables
This chapter shows how to compute basic descriptive statistics for a quantitative variable. You will learn the most popular measures of central tendency (the mean, the median and the mode) and dispersion (variance, standard deviation, range, IQR, median absolute deviation). The chapter will also demonstrate how to produce different graphs (box-and-whisker plots, histograms, density plots, Q–Q plots, line charts), which visualize univariate distributions and help one determine whether a variable is normally distributed. From the case studies you will learn how to analyse the distribution of word lengths in a sample, to detect suspicious values in subjects’ reaction times in a lexical decision task, and to correct some problems with the shape of a distribution.