T-Test

T-Tests Overview

• Single-sample t-test: One set of participants.

• Independent t-test: Two sets of participants.

• Paired samples t-test: One set of participants measured under two conditions.

Jamovi Practice

• Example Study: Psychology students at Elizabethtown College study an average of 2.5 hours/day.

• Research Question: Is there a difference in study hours compared to the general student population?

• Sample Data: 5 students reported studying hours: 2.5, 2, 1.5, 0.5, 1.

Conducting T-Tests in Jamovi

One-sample t-test

1. Select T-Tests > One Sample t test.

2. Add variable to the "Test variable" box.

3. Input null hypothesis value in "Test value" box.

Independent Samples t-test

1. Select T-tests > Independent Samples T Test.

2. Move variables to "Dependent Variables" or "Grouping Variable."

Paired Samples t-test

1. Select T-tests > Paired Samples T-Test.

2. Move variables to "Paired Variables".

Reporting Results in APA Style

• Report means (M), standard deviations (SD), t-statistics, degrees of freedom (df), p-values, and effect sizes (d).

• Example Report 1: Psychology majors (M = 1.50, SD = 0.79) studied less than general students, t(4) = -2.83, p = .047, d = -1.26.

• Example Report 2: Participants with invisibility cloak (M = 5.00, SD = 1.65) did not engage in more mischief than those without (M = 3.75, SD = 1.91), t(22) = -1.71, p = .101, d = -0.70.

• Example Report 3: After being given a cloak, participants engaged in more mischief (M = 5.00, SD = 1.65) compared to without (M = 3.75, SD = 1.91), t(11) = -3.80, p = .003, d = -1.10.

Practice Exercises

• Analyze the AfricaDrummingHK data set for:

  • Differences between pre and post self-report.

  • Overall change compared to 0.

  • Differences in overall change for individuals with and without Dementia.

  • Post self-report differences from a value of 2.