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Need Help With This One. Can someone please explain.

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by inavdeep » Tue Oct 08, 2013 8:12 am
If M is a negative integer and K is a positive integer, which of the following could be the standard deviation of a set {-7, -5, -3, M, 0, 1, 3, K, 7}?

I. -1.5
II. -2
III. 0


(A) I only (B) II only (C) III only (D) I and III only (E) None

Answer is E.
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by Brent@GMATPrepNow » Tue Oct 08, 2013 8:18 am
inavdeep wrote:If M is a negative integer and K is a positive integer, which of the following could be the standard deviation of a set {-7, -5, -3, M, 0, 1, 3, K, 7}?

I. -1.5
II. -2
III. 0


(A) I only (B) II only (C) III only (D) I and III only (E) None

Answer is E.
Nice question

The standard deviation is always greater than or equal to 0. So, ELIMINATE I and II.
The standard deviation equals 0 only when all of the values in the set are the same. This is clearly not the case, so the standard deviation cannot equal 0. ELIMINATE III.

This leaves us with E

Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
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