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
out that this estimate has a mean of (n-1/n) sigma^2. This can be corrected
by multiplying 1/n(sum i=1 to n)(xi - (x bar))^2
by a factor so that the estimate is
What is the factor?