GRE Subject Test: Math : Standard Deviation

Study concepts, example questions & explanations for GRE Subject Test: Math

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Example Questions

Example Question #531 : Gre Subject Test: Math

What is the standard deviation of the numbers 3, 5, 8, 9, and 10?

Possible Answers:

\displaystyle 5.14

\displaystyle 6.8

\displaystyle 3.49

\displaystyle 2.61

\displaystyle 6.3

Correct answer:

\displaystyle 2.61

Explanation:

The first step with standard deviation is to find the average or mean of the numbers. Add 3+5+8+9+10 together to get 35. Divide that by the number of scores, which is 5, to get a mean of 7.

Now, subtract the mean from each of the numbers

\displaystyle \\3-7=-4 \\5-7=-2 \\8-7=1 \\9-7=2 \\10-7=3

Next, square those values

\displaystyle (-4)^{2}=16

\displaystyle (-2)^{2}=4

\displaystyle 1^{2}=1

\displaystyle 2^{2}=4

\displaystyle 3^{2}=9

Now find the mean of these squared differences by adding the values and then dividing by the amount of numbers, 5 in this case.

\displaystyle 16+4+1+4+9=34

\displaystyle \frac{34}{5}=6.8

Finally, take the square root of this number to get the standard deviation.

\displaystyle \sqrt{6.8\displaystyle =2.61

 

 

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