A tale of two experiments

What is the best approach for each of the following experiments?

Experiment 1: You want to test the effect of alcohol on test scores of students. There are three conditions: the student consumed no alcohol, two glasses of beer, or five glasses of beer. Alcohol tolerance and time spent studying should also be considered somehow.

Experiment 2: You want to investigate the effects of certain fertilizers on plant growth. Assume you have two different fertilizers, A and B. Consider three conditions: you give the plant no fertilizer, fertilizer A, or fertilizer B. You measure the height of the plant after a specific period of time to see whether the fertilizers had an effect.

Possible answers

Use a between-groups design for both experiments.

Use a between-groups design for for Experiment 1 and within-subjects design for Experiment 2.

Use a within-subjects design for for Experiment 1 and between-groups design for Experiment 2.

Use a within-subjects design for both experiments.

Exercise

A tale of two experiments

Instructions

Possible answers