For each problem, select the best response.

(a) A study of the effects of running on personality involved 231 male runners who each ran about 20 miles a week. The runners were given the Cattell Sixteen Personality Factors Questionnaire, a 187-item multiple-choice test often used by psychologists. A news report (The New York Times, Feb. 15, 1988) stated, The researchers found statistically significant personality differences between the runners and the 30-year-old male population as a whole. A headline on the article said, Research has shown that running can alter one's moods. This study was

A. a double-blind experiment, but not a randomized experiment.
B. a randomized, double-blind experiment.
C. an observational study, but not an experiment.
D. an experiment, but not a double-blind experiment.

(b) Can pleasant aromas help a student learn better? Two researchers believed that the presence of a floral scent could improve a person's learning ability in certain situations. They had twenty-two people work through a pencil and paper maze six times, three times while wearing a floral-scented mask and three times while wearing an unscented mask. The three trials for each mask closely followed one another. Testers measured the length of time it took the subjects to complete each of the six trials. They reported that, on average, the subjects wearing the floral-scented mask completed the maze more quickly than those wearing the unscented mask, though the difference was not statistically significant. This study is

A. an observational study, but not an experiment.
B. an experiment, but not a double-blind experiment.
C. a double-blind experiment.
D. a convenience sample.