This chapter follows the same layout as the others with an introduction, purpose, and history of t-tests. The mechanics section focuses on the two tests used to determine if the difference in the means of two variables are statistically significant. These two tests are the independent and dependent samples t-tests. Each test section includes an explanation of the equation, introduces the idea of standard error, and explains how to determine if significance exists in the results. The chapter then includes a step-by-step guide to run a t-test in SPSS and R and how to interpret the results. The chapter ends with two planning research examples that use t-tests.