A Random Sample of Size N Has Been Selected from a Normally

Short Answer

A random sample of size n has been selected from a normally distributed population whose standard deviation is s. In estimating an interval for the population mean, the t-distribution should be used instead of the z-test if: $\begin{array}{|l|l|}\hline A&\text { \( n \geq 30 \) and \( \sigma \) is known}\\\hline B&\text {\( \sigma \) is unknown and estimated by \( s \), and the population is normal. }\\\hline C&\text { Population is normal and \( \sigma \) is known.}\\\hline D&\text {None of these choices are correct. }\\\hline \end{array}$