The following MINITAB output presents a confidence interval for a population mean.
$\begin{array}{crrrrc}
\hline \text { Variable } & \mathrm{N} & \text { Mean } & \text { StDev } & \text { SE Mean } & 99 \% \mathrm{CI} \
\mathrm{x} & 72 & 84.4238 & 33.8186 & 3.9856 & (73.874,94.973) \
\hline
\end{array}$
How many degrees of freedom are there?
A) 3.9856
B) 72
C) 73
D) 71

Question

Quizplus · Accepted Answer

The degrees of freedom for a confidence interval for a population mean, when the sample standard deviation is used as an estimate for the population standard deviation, is calculated as the sample size minus one. Here, N = 72, so the degrees of freedom are 72 - 1 = 71.

The Following MINITAB Output Presents a Confidence Interval for a Population