Hoping to Reduce the Waiting Time, a Doctor's Office Tried $\text { Mann/Whitney Test }$

Multiple Choice

Hoping to reduce the waiting time, a doctor's office tried a new way of scheduling its appointments. Populations of waiting times are believed to be similar except in central tendency. However, waiting times may not be normally distributed, so a nonparametric test was chosen to compare the waiting times. The Wilcoxon/Mann-Whitney test results are shown below: $\text { Mann/Whitney Test }$

$\begin{array}{|c|c|c|}\hline\text { n }&\text { sum of ranks }\\\hline 21 & 600.5& \text { Old Way}\\\hline 25 & 480.5& \text { New Way}\\\hline 46 & 1081& \text { Total}\\\hline\end{array}$

$493.50$ expected value
$45.31$ standard deviation
$2.35 \mathrm { z }$ , corrected for ties
$.0094 \mathrm { p }$ -value (one-tailed, upper) Which is the best conclusion?

A) The medians differ at ? = .01.
B) The means differ at ? = .01.
C) The samples differ at ? = .01.
D) There are no differences at ? = .01.