Evidence guide
Understanding Statistical Significance
A small p-value measures compatibility with a statistical null model; it does not measure importance or truth.
What p < 0.05 does
Under stated assumptions, it says data at least this extreme would be relatively uncommon if the null model were true.
What it does not do
It does not give the probability that the hypothesis is true, prove causation or show the effect is large enough to matter.
Read the interval
Effect size and confidence or credible intervals show magnitude and uncertainty. Multiple testing, flexible analysis and small samples can make isolated significance fragile.
A practical reading checklist
- How large is the effect?
- How wide is the uncertainty interval?
- How many outcomes were tested?
- Was the analysis prespecified?