researcher wants to examine the effects of caffeine on working memory for college students. He randomly places subjects into three groups: no caffeine (N = 37), 100mg of caffeine - or about one cup of coffee (N = 43), and 200mg of caffeine - or about two cups of coffee (N = 39). He then administers a working memory test to each subject, with scores ranging from 0-100. He finds that the 200mg group performs the best (average score of 87.38), followed by the 100mg group (72.36), and then the no caffeine group (71.28). Statistical analyses indicate that these differences are statistically significant in that the 200mg group performs significantly better than either of the other two groups.

1. What is the independent variable in this study?

2. What is the dependent variable in this study?

3. What is the total sample size?

4. Who is the population?

5. Is this an experiment or observational study?

6. Whatare the null and alternative hypotheses?