Definition

Statistical significance

The convention of treating a result as unlikely to be pure chance when its p-value falls below a preset threshold, usually 0.05.

Calling a result "statistically significant" means one thing: under the null hypothesis, data this extreme would occur less often than the chosen alpha level (usually 5%). The threshold is a social convention, not a law of nature — 0.049 and 0.051 are nearly identical evidence.

Significance says nothing about size or importance; with enough participants, trivial differences become significant. Modern practice reports the exact p-value, the effect size, and the confidence interval, and lets readers judge the evidence rather than the binary verdict.