You want to test the hypothesis that a brief mindfulness meditation exercise improves test performance under time pressure, but not when there is no time pressure. You conduct a study in which you experimentally manipulate mindfulness meditation (meditation or no meditation) and time pressure (time pressure or no time pressure) and measure test performance in a between-subjects post-test design with 100 people.

1. What is/are the independent variables and dependent variables? Levels of the independent variable(s)?

2. What kind of claim can you make from this study design? (frequency, association, or causal)? 

3. Draw line graphs that depict the following results. For each figure explain what the results show for the main effects and the interaction, in your own words: 

a. Main effect of time pressure, no main effect of meditation, no interaction

b. Main effect of meditation, no main effect of time pressure, no interaction

c. Two main effects and no interaction

d. Main effect of meditation, no main effect of time pressure, an interaction

e. Main effect of time pressure, no main effect of meditation, an interaction

f. No main effects and an interaction

4. Now redesign the study using a between-subjects pre- and post-test design. Describe the design here, and describe one potential strength and one potential weakness of this design compared to a post-test only design.

5. Now redesign the study using a within-subject repeated-measures design. Describe the design here, and describe one potential strength and one potential weakness of this design compared to a between-subjects design.

6. Evaluate the study as you are imagining it in terms of the four validities (construct validity, external validity, statistical validity, and internal validity).