What does it mean when we say “within-subjects designs are experiments that are run on a single group of participants”? How can this statement be reconciled with the requirement that the independent...

What does it mean when we say “within-subjects designs are experiments that are run on a single group of participants”? How can this statement be reconciled with the requirement that the independent variable must be present at more than one level in experiments?

Assume you have 60 participants for a study. Use the table of random numbers (Appendix: Random Numbers) to assign participants randomly to three conditions with 20 participants in each condition.