After reading this chapter, you should be able to do the following:

• Identify when a related samples t test should be used
• Explain the advantages of using a related samples design over an independent samples design
• Explain the logic of the related samples t test
• Write null and research hypotheses using symbols and words for both one- and two-tailed tests
• Compute the degrees of freedom and define the critical region for one- and two-tailed tests
• Compute a related samples t test by hand (using a calculator) and using SPSS
• Determine whether you should reject the null hypothesis
• Compute an effect size (d) and interpret it
• Summarize the results of the analysis using American Psychological Association (APA) style
• Interpret the SPSS output for a related samples t test