In an Experiment Designed to Study the Effects of Illumination

Essay

In an experiment designed to study the effects of illumination level on task performance, subjects were required to insert a fine-tipped probe into the eyeholes of ten needles in rapid succession both for a low light level with black background and a higher level with a white background. Each data value is the time (sec) required to complete the task.
Subject $$\begin{array} { l c c c c c c c c c } \hline & \mathbf { 1 } & \mathbf { 2 } & \mathbf { 3 } & \mathbf { 4 } & \mathbf { 5 } & \mathbf { 6 } & \mathbf { 7 } & \mathbf { 8 } & \mathbf { 9 } \\\hline \text { Black } & 28.85 & 31.84 & 35.05 & 28.74 & 23.89 & 44.05 & 28.01 & 27.96 & 30.47 \\\text { White } & 21.23 & 23.84 & 25.96 & 22.68 & 22.50 & 27.98 & 19.61 & 19.07 & 27.59 \\\hline\end{array}$$ Does the data indicate that the higher level of illumination yields a decrease of more than 5 sec in
true average task completion time? Test the appropriate hypotheses using the Wilcoxon test.