LEARNING OBJECTIVES

CHAPTER OVERVIEW

In the last chapter, the logic of hypothesis testing was introduced with the single-sample z test. The single-sample z test was great as a prototype of hypothesis testing, but it is rarely used because it requires knowing the population standard deviation of the dependent variable. For most psychological variables—for example, reaction time in a driving simulator, number of words recalled from a list of 20, how close one is willing to get to a snake—the population standard deviation isn’t known. In this chapter, we’ll learn the single-sample t test, a test that like the single-sample z test allows one to compare a sample mean to a population mean. The single-sample t test, unlike the single-sample z test, can be used when a researcher doesn’t know the population standard deviation. Thus, it is a more commonly used test.