Set S has a mean of 9 and a standard deviation of 1.5. We are going to add two additional numbers to Set S. Which pair of numbers would decrease the standard deviation the most? Select
A) {2, 10}  B) {16, 16}  C) {9, 11}  D) {7, 13}  E) {10, 18}
answer A, B,C, and D mean is not 9 therefore not accepted . E mean is 9 but S.D is one unit. therefore accepted   answer is E mean is 9 and S.D decreases minimum.   {10, 18}
<result>E</result>
Set S has a mean of 9 and a standard deviation of 1.5. We are going to add two additional numbers to Set S. Which pair of numbers would decrease the standard deviation the most?