For the following studies, state whether estimation or hypothesis testing is required. Also, is an independent- or a repeated-measures t statistic appropriate?

a. An educator wants to determine how much mean difference can be expected for the population in SAT scores following an intensive review course. Two samples are selected. The first group takes the review course, and the second receives no treatment. SAT scores are subsequently measured for both groups.

b. A psychiatrist would like to determine whether a new medication has any effect on psychotic symptoms. A sample of patients is assessed and then placed on drug therapy for 2 weeks. The severity of their symptoms is assessed again at the end of the treatment.

c. A researcher would like to determine how much people's moods are affected by seasonal changes. A sample of 100 adults is obtained and each individual is given a mood-analysis problemnaire in the summer and again in the winter.

d. A researcher would like to determine whether participation in sports has an effect on self-esteem for high school students. The researcher obtains a sample of 50 students who are active in varsity sports and a comparison sample of 50 students who do not participate in any high school sports. Each student is given a self-esteem problemnaire.