7.12 MRIs In a study described in the American Journal of Sports Medicine, Peter D. Franklin and col- leagues reported on the accuracy of using magnetic resonance imaging (MRI) to evaluate ligament sprains and tears on 35 patients. Consecutive patients with acute or chronic knee pain were selected from the clinical practice of one of the authors and agreed to participate in the study.

a. Describe the sampling plan used to select study participants.

b. What chance mechanism was used to select this sample of 35 individuals with knee pain?

c. Can valid inferences be made using the results of this study? Why or why not?

d. Devise an alternative sampling plan. What would you change?