The Sorbinil Retinopathy Trial was conducted among 497 type l (insulin-dependent) diabetic patients who had little or no evidence of retinopathy at baseline. Retinopathies are abnormalities of the retina that sometimes occur among diabetic patients and can result in advanced stages in substantial losses of vision. Patients were randomized to either Sorbinil an aldose-reductase inhibitor, or placebo and were seen at 1 year and then every 9 months up to 48 months after randomization. In addition, all subjects had a final visit at the end of the trial (max=56 months). Sixteen of the patients provided no follow up. The primary endpoint of the trial was based on change in retinopathy severity level from baseline to maxiumum follow up (i.e. severity level at grading scale was used to evaluate change; 2+ levels vetter, 1 level better, no change, 1 level worse ..., 5+ levels worse. The outcome data by treatment group are given in table 10.52. The primary outcome for the study was worsening by 2 or more levels.
What test can be used to compare the two treatment groups on the primary endpoint?
Implement the, and provide a p value (two tailed).
A more efficient method of analysis would leve the change in retionopathy level in its raw form without grouping the data but would take into account the ordinal nature of the change scores.
What test can be used to compare the two groups if this more efficient method is used.
Implement the test and provide a p value two-tailed.