family-wise error rate

Family-wise error rate (FWER) is the probability of making at least one false positive (incorrectly finding an effect) among multiple statistical tests conducted simultaneously. When many tests are performed, the chance of obtaining at least one false positive increases. FWER controls this risk, ensuring that the overall chance of any incorrect conclusion remains within a predefined threshold (usually 5%). In simple terms, it helps researchers avoid mistakenly identifying effects that are actually due to random chance when analyzing many hypotheses at once.