I need help with the mean estimation for a research study proposal.

To measure the effectiveness of the role-play intervention, a between-subjects t-test, and repeated measures t-test will be utilized. The dependent variable will be the self-advocacy skills which the sample will gain, and the independent variable is the role-play intervention implemented. The t-tests will be computed through the SPSS software.

Sample (N = 300)

These are the expected results

After the intervention is implemented in the first group, they will show an increase in self-advocacy skills. After the intervention is implemented in the second group, they will show an increase in self-advocacy skills, and the first group will show that they have retained their self-advocacy skills from the first time the intervention was administered.

How would you estimate the mean differences?