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21 Mar 2018, 23:04
Kudos
Bookmarks
C
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
5%
(low)
Question Stats:
93% (00:51) correct
7%
(00:26)
wrong
based on 57
sessions
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Not Attempted Yet
The distribution of the scores on a standardized test is bell-shaped and is symmetric about its mean, M, with a standard deviation, S. If 68% of the scores fall between M - S and M + S, what percent of the scores are greater than M + S?
(A) 4%
(B) 8%
(C) 16%
(D) 32%
(E) 34%
(A) 4%
(B) 8%
(C) 16%
(D) 32%
(E) 34%
23 Mar 2018, 12:46
Kudos
Bookmarks
Bunuel
Since 68% of the scores fall between M - S and M + S, then 32% of the scores fall in the two tails of the bell curve. Since the distribution is symmetric about its mean, that means exactly half of 32%, i.e., 16%, of scores fall above M + S (and the other 16% fall below M - S).
Alternate Solution:
Since the distribution is symmetric about its mean, exactly half of 68%, i.e. 34% of the scores fall between M and M + S (and the other 34% fall between M and M - S). Again since the distribution is symmetric about its mean, 50% of the scores fall above M. Then, 50 - 34 = 16% of the scores fall above M + S.
Answer: C
