Question: Musculoskeletal neck-and-shoulder disorder is common among office staff who perform repetitive tasks using visual display. The article “Upper-Arm Elevation during Office Work” (Ergonomics, 1996: 1221 1230) reported whether more varied work condition would have impact on arm movement. Each observation is the amount of time, expressed as a proportion of total time observed, during which the arm elevation was below 30°. The two measurements from each subject were obtained 18 months apart.

Subject: 1 2 3 4 5 6 7 8 9 10

Before : 81 87 86 82 90 86 90 73 74 75

After: 78 91 78 78 84 67 92 70 58 72

Subject: 11 12 13 14 15 16

Before: 72 80 66 72 56 82

After: 70 58 66 60 65 73

How do you check the normality assumption?

Does the data suggest that the true average time during which elevation is below 30° differ after the change from what it was before the change?

Does it appear that the change in work conditions decrease true average time by more than 5?