We may not be able to generalize the fi ndings of Daniel Levinson, the researcher who studied the midlife crisis in the 1970s, to the population at large because his initial observations were based on...

We may not be able to generalize the fi ndings of Daniel Levinson, the researcher who studied the midlife crisis in the 1970s, to the population at large because his initial observations were based on

 a. a questionnaire survey of 400 men.

 b. an intensive study of only 40 men.

 c. a cross-sectional questionnaire study of men and women in several age groups.

 d. a study of poorly educated men from three different countries.