A survey of 47 sophomores investigated the effect of studying and extracurricular activities on grades:

where Y = grade point average on a four point scale; X = average hours per week spent studying; D = 1 if the person spends at least 10 hours a week on an extracurricular activity, such as work or sports, and 0 otherwise; and the standard errors are in parentheses. The researcher concluded “The effect of extracurricular activity is not significant and does not lend support to the commonly held notion that extracurricular activity negatively affects grades because it reduces available study time.” Carefully explain why the coefficient of D does not measure the extent to which extracurricular activity affects grades by reducing available study time.

Transcribed Image Text:

Y= 2.936 +0.023X-0.028D (0.113) (0.006) (0.096)