Twin studies suggest that ____ factors play the largest role in accounting for ADHD

A researcher discussing the prevalence of eating disorders makes reference to what she says is a cohort effect for these disorders. What does this mean?

a. Eating disorders tend to run in close-knit families. b. Women born after 1960 have a higher rate of bulimia nervosa than women born prior to 1960. c. Families that place a special emphasis on eating meals together have high rates of eating disorders. d. The frequency of eating disorders is strongly related to the rate among friends, especially in high school.

In order to prevent the researcher's expectations from influencing study participants, a(an) _____ design is used

a) anonymous b) quasi-experimental c) computerized d) double-blind