M03-34
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08 Jul 2019, 10:12
The standard deviation measures how far a set of values are from the average of that set.
In order to calculate the standard deviation of a set, do the following:
1) Find the mean of the set
2) Subtract each term from the mean
3) Square each number obtained in step 2
4) Find the mean of the values in step 3
5) Take the square root of the mean in step 4
Now, we won't be expected to do this on the GMAT, but we will be expected to recognize some patterns.
Back to the question:
set A={10, 12, 14, 16, 18, 20, 22, 24, 26, 28}
I. Set B={1,2,3,4,5,6,7,8,9,10}
The terms in this set are closer to each other than the terms in set A, therefore the standard deviation of set B is less than the standard deviation of set A.
II. Set C={1,3,5,7,9,11,13,15,17,19}
The terms in this set are as spaced out as the terms in set A, therefore the standard deviation of set C is the same as the standard deviation of set A.
III. Set D={2,3,5,7,11,13,17,19,23,29}
The terms in this set are more spread out than the terms in set A, therefore the standard deviation of set D is greater than the standard deviation of set A.
The answer is C.