Question

$\mbox{The mean of a set of test scores is 86 and the standard deviation is 3. }$

Answer 1

For a normally distributed data set, approximately 68.27% of the data is within one standard deviation. i.e. approximately 0.6827 x 200 = 137 test scores is between 86 + or - 3 i.e. from 83 to 89. Hence approximately 137/2 = 68 test score is within the 86 to 89 range.