This chapter focuses on measurement, which provides rules about assignment of numbers and symbols to the levels of variables, and on descriptive statistics, which summarize and describe data from a sample without making inferences about the larger population from which the sample data were drawn. We begin by providing a brief overview about the normal or bell-shaped curve. As you will see throughout the chapter and in later ones, whether the responses or scores on a variable are distributed normally is important in the selection of appropriate statistics. Thus, understanding what is meant by normally distributed (or normal) data is important for measurement and for the use of appropriate descriptive statistics and graphs.