According to Microsoft Excel Help:
VAR uses the following formula:
where x is the sample mean AVERAGE(number1,number2,…) and n is the sample size.
Shouldn't it be n, rather than n - 1, in the denominator?
Use VARP for the variance you want ("population variance"). VAR is the unbiased estimator for a normally distributed population.
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Use VAR (with n-1 denominator) when you wish to estimate the variance of the underlying population from the sample, or VARP (with n denominator) when the sample is the population.
I find the name "population variance" quite ambiguous...