For a 4 -unit class like Statistics , students should spend average of 12 hours studying for the class . A survey was done on 30 students , and the distribution of total study hours per week is bell - shaped with a mean of 14 hours and a standard deviation of 3 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 .
