A Random Sample of 64 Observations Has a Mean of 30

Short Answer

A random sample of 64 observations has a mean of 30. The population variance is assumed to be 9. The 85.3% confidence interval estimate for the population mean (to the third decimal place) is: $\begin{array}{|l|l|}\hline\text { A. } & 28.369 \pm 31.631 . \\\hline \text { B. } & 29.456 \pm 30.544 . \\\hline \text { C. } & 28.560 \pm 31.440 . \\\hline \text { D. } & 29.383 \pm 30.617 . \\\hline\end{array}$