Needed a class's exam scores are normally distributed. if the average score is 65 and the standard deviation is 6, what percentage of students scored below 71? hint: use the 68-95-99.7 rule. a)34% b)50% c)68% d)84%

The answer is Letter D - 84%

68% of the data is within +/- 1 SD from the mean = 59 to 7195% of the data is within +/- 2 SDs from the mean = 53 to 7799.7% of the data is within +/- 3 SDs from the mean = 47 to 83

The whole 68% (59 - 71) scored below 71. Since the data are evenly distributed, we'll get the 32% (100 - 68) outside the range of 68% and divide it by 2 and add the quotient to the original 68% so that we'll get the total data below 71.
   100 - 68 = 32
   32 / 2 = 16
   16 + 68 = 84