Physicians use a variety of quantitative sensory testing (QST) tools to assess pain in patients, but there is concern about the consistency of such tools. The article “Test-Retest Reliability of [QST] in Knee Osteoarthritis and Healthy Participants” (Osteoarthritis and Cartilage 2011: 655–658) describes a study in which participants’ responses to various stimuli were measured and then re-measured one week later. For example, pressure was applied to each subject’s knee, and the level (kPa) at which the patient first experienced pain was recorded.
a. Pressure pain measurements were taken twice on each of 50 patients with osteoarthritis in the examined knee. The Wilcoxon signed-rank test statistic value computed from this paired data was s₊ = 616. Use a two-sided, large-sample test to assess the reliability of the sensory test at the .10 significance level.
b. The same measurements were made of 50 healthy patients, and the resulting test statistic value was s₊ = 814. Carry out the test indicated in part (a) using this information. Does the pain pressure test appear reliable for the population of healthy patients?