A researcher is interested in the determinants of academic performance. Suppose the population model is:
score = 30 + 0.2*attend + 0.3*effort + u
score: student’s score in the course

Attend: student’s class attendance rate (in percent)
Effort: student’s effort level (on a scale from 0 to 100)
Suppose it is a known fact that students who spend more effort tend to attend classes more frequently.

(a) If you run a regression of score on attend only, what kind of problems will you get? Explain briefly.
(b) If you run a regression of score on attend, effort, and gender (=1 if male, =0 otherwise), what kind of problems will you get? Explain briefly.