People make all kinds of assumptions—guesses, really—about how things work in organizations. Most of these guesses are rooted in sample bias. A textbook illustration of sample bias is Abraham Wald’s work in World War II. Wald, a Hungarian mathematician, was a member of the Statistical Research Group (a group based at Columbia University that took on statistical assignments from the US government during the war). He was asked what the military could do to improve the survival rates for bombers. Wald reviewed the location of bullet holes on planes returning from bombing runs to determine where
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