A Random Sample of 15 Automobile Mechanics Certified to Work

Essay

A random sample of 15 automobile mechanics certified to work on a certain type of car was selected, and the time (in minutes) necessary for each one to diagnose a particular problem was determined, resulting in the following data: $$\begin{array} { l l l l l l l l } 32.6 & 32.1 & 17.6 & 28.7 & 29.1 & 27.4 & 37.0 & 32.8 \\33.9 & 55.2 & 14.5 & 25.2 & 10.8 & 26.9 & 32.2 &\end{array}$$ Use the Wilcoxon test at significance level .10 to decide whether the data suggests that "true" average diagnostic time is less than 32 minutes.