Posthoc

Posthoc is a Latin term that translates roughly to “after this.” In general usage, it appears in two main contexts: logic and statistics. In logical reasoning, the phrase is part of the expression post hoc ergo propter hoc, describing a common fallacy in which it is assumed that because one event followed another, the first caused the second. This conflates correlation with causation and can mislead causal inferences unless supported by additional evidence, control of confounding factors, or experimental manipulation.

In statistics, post hoc refers to analyses or tests conducted after an initial analysis has yielded a significant result. Post hoc tests are used to explore which specific groups differ from one another following an analysis of variance (ANOVA). Common methods include Tukey’s HSD, Bonferroni, Scheffé, and Holm adjustments, which aim to control the familywise error rate when multiple comparisons are made. While useful for exploratory investigation, post hoc tests are typically considered less robust than pre-planned contrasts and their results should be interpreted with caution, as they increase the risk of false positives if not properly adjusted or reported transparently.

Etymologically, post hoc is Latin for “after this,” reflecting its use to describe analyses that occur after an initial finding. The term is widely used across disciplines such as psychology, biology, and economics, where researchers distinguish between pre-planned (a priori) analyses and post hoc explorations.