For a 4-unit class like Statistics, students should spend average of 12 hours studying for the class. A survey was done on 27 students, and the distribution of total study hours per week is bell-shaped with a mean of 14 hours and a standard deviation of 2.8 hours.

Use the Empirical Rule to answer the following questions.

a) 68% of the students spend between
hours and
hours on Statistics each week.

b) 95% of the students spend between
hours and
hours on Statistics each week.

c) 99.7% of the students spend between
hours and
hours on Statistics each week.