Introduction to Evidence-Based Medicine

William J. Powers, M.D.-- Departments of Neurology, Neurosurgery and Radiology
Washington University School of Medicine -- Presented July 11, 2006

Translating Evidence into Patient Care:
 The Perils of Subgroup Analysis
 

                      • Negative Trials with ”positive” subgroups

                          ◊ Increased Type I error due to multiple comparisons

                      • Positive Trials with “negative” subgroups

                          ◊ Increased Type II error due to reduced power
                               from smaller sample size

 
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