To obtain an estimate for the variance of the population mean,

sigma^2, a natural idea would be to calculate

1/n(sum i=1 to n)(xi - (x bar))^2

.

It turns

out that this estimate has a mean of(n-1/n) sigma^2. This can be corrected

by multiplying1/n(sum i=1 to n)(xi - (x bar))^2

by a factor so that the estimate is

unbiased.

What is the factor?