The American Economic Review (Dec. 2008) published a study on whether the removal of credit constraints would impact the likelihood of a student dropping out of college. As part of the investigation, the researchers looked for factors other than credit constraints that would influence the college dropout decision. One factor of interest was expected GPA for a college student who studied 3 hours per day. In a representative sample of 307 college students, the researchers reported the following summary statistics for the expected GPA of those who studied 3 hours per day:  = 3.11, s = .66.
a. Give an interval that will contain most (at least 75% to approximately 95%) of the 307 GPAs.
b. If you observe a GPA of 1.25, is it likely that this college student studied 3 hours per day? Explain.