sharath.chalamgari (1/28/2011)

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but if i cange the Query with some where condition,where i will get only one Row (sample) then the stdevp will results the null value

select stdev(pa_Rates) From Package where pa_PackageID = 1

Koen (da-zero) (1/28/2011)

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The WHERE clause is executed first, so you are still calculating the variance over 1 row, hence the NULL.

sharath.chalamgari (1/28/2011)

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Ya that's what i have explained above.

mdv 9731 (1/28/2011)

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I do not agree that the answer is right.
Think it is supposed to be 0.

the standard deviation σ (sigma) is the square root of the average value of (X − μ)2.

Which means σ = sqrt(((1-1)^2)/1) = 0

Or in other words std. deviation equals sqrt of (population-avarage) sq / number of population values

Please correct me if im wrong on the formula it has been a while since i used my statistics