Guide SPSS How to: Calculate the independent t-test

Step-by-Step Guide

1. Open your SPSS data file.
2. Click on “Analyze” in the top menu, then select “Compare Means” > “Independent-Samples T Test”
3. In the dialog box that appears:

• Move your dependent variable (continuous) into the “Test Variable(s)” box.
• Move your independent variable (categorical with two groups) into the “Grouping Variable” box

1. Click on the “Define Groups” button next to the Grouping Variable box
2. In the new window, enter the values that represent your two groups (e.g., 0 for “No” and 1 for “Yes”)[1].
3. Click “Continue” and then “OK” to run the test

Interpreting the Results

1. Check Levene’s Test for Equality of Variances:

• If p > 0.05, use the “Equal variances assumed” row.
• If p ≤ 0.05, use the “Equal variances not assumed” row

1. Look at the “Sig. (2-tailed)” column:

• If p ≤ 0.05, there is a significant difference between the groups.
• If p > 0.05, there is no significant difference

1. If significant, compare the means in the “Group Statistics” table to see which group has the higher score

Tips

• Ensure your data meets the assumptions for an independent t-test, including normal distribution and independence of observations
• Consider calculating effect size, as SPSS doesn’t provide this automatically