Problem Solving - 42

E is a collection of four odd integers and the greatest difference between any two integers in E is 4. The standard deviation of E must be one of how many numbers?

(A) 3
(B) 4
(C) 5
(D) 6
(E) 7


Answer: B

Suppose the integers are 1, 3 and 5. Therefore the four integers can be:

1, 5, 5, 5
1, 3, 5, 5
1, 3, 3, 5
1, 1, 5, 5
1, 1, 1, 5
1, 1, 3, 5

Here two pairs have the same standard deviation. thus in all we have four different standard deviations