1. says that 1 standard deviation above and below the mean ranges from 7 to 13. Calculate the range. Range=6.

Now, standard deviation for a set is constant. Let us draw a number line.

~~---------|----------------|---------------|------------------~~ -m mean +m

In this line segment, mean is at the center and the distance between 2 equal points -m and +m from mean is 6. These two points are equidistant as they are mentioned to be one standard deviation above and below the mean. Hence, the range of values between them=2m

2m=6

Hence, m=3

Hope this clarifies any doubts!

Sachin9 wrote:

watwazdaquestion wrote:

smartass666 wrote:

Given that the mean of Set A is 10, what is the range of two standard deviations above and below the mean?

(1) One standard deviation above and below the mean ranges from 7 to 13.

(2) The median of set A is 11.

1. standard deviation = 3 since mean = 10... 3 units below and 3 units above. can calculate range of 2 standard deviations above and below mean by: 10-6 = 4 and 10+6 = 16... range of 2 standard deviations above and below mean = (4, 16)

2. gives no information on standard deviation. insufficient.

answer is A

how did u calculate the standard deviation to be 3?

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Thanks

Kris

Instructor at Aspire4GMAT

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