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 1 2 3 4 5 6 7 8 9
Black 25.01 41.05 27.47 25.74 24.96 28.84 25.85 20.89 32.05
White 16.61 24.98 24.59 19.68 16.07 20.84 18.23 19.50 22.96
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 P-value approach.