How Statistics Can Save Your Life or End It : A Course Module

Probability and statistics are powerful weapons that can help people make good decisions, but that can also be used to wreak havoc. This paper is the first in a series designed to provide examples to students of how statistics can be used and misused to mislead the public and result in poor decision-making. In this module, we discuss the use of statistics in evaluating healthcare decisions, and how they can mislead patients. This particular module, therefore, is also of use to patients who wish to understand how to use statistics to evaluate treatment options. A patient deciding whether to take a prescription drug or undergo a medical procedure should understand basic evaluation criteria like the number needed to treat (NNT) and number needed to harm (NNH), which are described in this paper. We also describe how information presented to consumers regarding the efficacy of drugs often focuses on the wrong statistical measures. Brochures and advertisements for medications often focus on the relative risk reduction (RRR), when NNT is more helpful in evaluating the efficacy of a treatment