The diagnosis of schizophrenia requires that signs of the disorder are present continuously

A tennis coach believes orange juice improves performance. She gives her players orange juice on randomly chosen days, and rates their performance. What, if anything, is wrong with this study? a. People in a control group should drink orange juice on the same days. b. The players should be able to choose when to drink orange juice

c. The study should have a blind observer. d. Nothing is wrong with this study.

A psychologist is working on a book about student reactions to success and failure on exams. If he does a good job of researching the topic, he will find each of the following personality variables except one is useful in predicting the students' behavior. Which one?

A. Extraversion-introversion B. Self-esteem C. Locus of control D. Explanatory style