ABSTRACT
This chapter is all about t tests. The chapter begins with a description of the family of t distributions. These are similar to the normal distribution, but their shape is influenced by the sample size, with a flatter peak in the middle and more extreme cases as the sample sizes decrease. Next, the chapter briefly introduces three kinds of t tests: one-sample, independent samples, and dependent (or paired) samples t tests. After these brief introductions, each of these three types of t tests are discussed in depth, including discussions of the conceptual issues of each as well as illustrations of how to calculate and interpret each kind of t test. In the in-depth section on independent t tests, a brief description of the different ways of calculating the standard error of the difference between the means, depending on whether the sample sizes are equal between the two groups, is presented. Because t tests are part of the family of inferential statistics, the chapter includes a discussion of hypothesis testing, probability, statistical significance tests, and effect sizes for the t tests. In addition, examples of output from t tests conducted using the Statistical Package for the Social Sciences (SPSS) software program are presented and interpreted for independent and dependent t tests.
