1.To determine whether cramming can increase GRE scores, a researcher randomly assigns college students to either a specialized GRE test-taking workshop, a general test-taking workshop, or a control (non-test-taking) workshop. Furthermore, to check the effect of scheduling, students are randomly assigned, in equal numbers, to attend their workshop either during a marathon weekend or during a series of weekly sessions.

2.A criminologist suspects that there is a relationship between the degree of structure provided for paroled ex-convicts (a supervised or unsupervised “rehab” house) and whether or not there is a violation of parole during the first 6 months of freedom.

3.A psychologist uses chimpanzees to test the notion that more crowded living conditions cause aggressive behavior. The same chimps live in a succession of cages containing one, several, or many other chimps. After several days in each cage, chimps are assigned scores on the basis of their aggressive behavior toward a chimp like stuffed doll in an observation cage.

4.In an extrasensory perception experiment involving a deck of special playing cards, each of 30 subjects attempts to predict the one correct pattern (on each playing card) from among fi ve possible patterns during each of 100 trials. The mean number of correct predictions for all 30 subjects is compared with 20, the number of correct predictions per 100 trials on the assumption that subjects lack extrasensory perception.