The Sample Variance $s ^ { 2 }$ Is an Unbiased Estimator of the Population Variance

Short Answer

The sample variance $s ^ { 2 }$ is an unbiased estimator of the population variance $\sigma ^ { 2 }$ when the denominator of $s ^ { 2 }$ is: $\begin{array}{|l|l|}\hline\text { A. } & n . \\\hline \text { B. } & n-1 \\\hline \text { C. } & \sqrt{n } \\\hline \text { D. } & n+1 \\\hline\end{array}$