GRE - Standard Deviation

The frequency distributions shown above represent two groups of data. Each of the data values is a multiple of 10.

Quantity A = The standard deviation of distribution A
Quantity B = The standard deviation of distribution B

A) Quantity A is greater.
B) Quantity B is greater.
C) The two quantities are equal.
D) The relationship cannot be determined from the information given.

How to answer just by looking at the diagram without doing tedious calculations?

• Hm, you probably have to do the calculation, but that's very easy with the given data. At least to me it looks to close to eyeball it - maybe that's just me. – Stefan Mesken Aug 15 '14 at 8:22

First of all, see that both the distributions are symmetric - So the median would be the center value, which is $30$
Since standard deviation measures spread of the data, $B$ will be having a greater standard deviation because more data values in $B$ are away from the median compared to $A$
• thats a very good question! the short answer is : $\text{mean = median}$ for symmetric distributions – ganeshie8 Aug 15 '14 at 8:30