# Math Help - Calculating standard deviation

1. ## Calculating standard deviation

Hi, Given sample size as 25 and mean as 56, can any one of you help me calculating standard deviation?

2. ## Re: Calculating standard deviation

Hey pmishra.

You need to have information about the sample. If you have the sample just add up the sums of squares (i.e. (x_i - mean)^2) for every i from 1 to 25 and divide that total answer by n - 1 (n = 25) in your case.

3. ## Re: Calculating standard deviation

Remember that standard deviation is also called root mean square deviation. That means square root of the mean of the squares of deviation.

4. ## Re: Calculating standard deviation

The standard deviation of returns is important to investors because it is the standard measure of investment risk, and investment risk is the degree of uncertainty of earning the expected rate of return. As you will see, the standard deviation of returns can be used to estimate the probability of the return on an investment falling within a given range relative to the expected rate of return in any given period.

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5. ## Re: Calculating standard deviation

Originally Posted by pmishra
Hi, Given sample size as 25 and mean as 56, can any one of you help me calculating standard deviation?
No. Given any $\sigma> 0$ you can construct a sample, of size 25 and mean 56, having that standard deviation.