Incorrect use of the student t test in randomized trials of bilateral hip and knee arthroplasty patients.

The statistical analysis of a study's results is critical to its interpretation. Often confused, 2 types of t tests exist for dependent or independent samples. We reviewed randomized controlled trials that included patients undergoing bilateral total hip or knee arthroplasty (dependent samples) that used the t test for analysis. Our inclusion criteria resulted in 40 studies for review, 10 of which combined both unilateral and bilateral patients. Of the 30 studies that compared a pure sample of only bilateral patients, 18 (60%) incorrectly used the independent t test. Of the 10 studies with mixed samples, 8 (80%) used the independent t test. The extent to which the incorrect use of this statistical test led to misleading conclusions is uncertain; however, our findings highlight the misuse of statistical tests in the arthroplasty literature.