# Standard Deviation from IPSLA values

I have a question about some of the values that can be pulled from IPSLA. We would like to calculate the standard deviation for the mean jitter values. I see several references to using values provided by ip sla (ie Sum2) to calculate this but the way it reads that doesn't seem quite right to me. Does the Sum2 value = the sum of each (value - mean) squared? The way it reads to me is that it is the sum of the each value squared. I'm not sure how the latter would be useful.

If the first case is true then I should be able to just calculate the square root of Sum2/Number and I'm good but I want to confirm that this is accurate.

**Correct Answer**by Joe Clarke about

*6 years 10 months*ago

It depends on the sample size. The formula:

Will give you an estimation of the closeness of the sample stddev to the actual. A sample size of 10,000 gives you a 1% margin of error.