Confidence intervals and p-values
A confidence interval describes the range of parameter values supported by a procedure under its statistical assumptions. A p-value quantifies how incompatible the observed data are with a specified null model.
Open interactive lesson & self-check ↗Confidence interval: effect and uncertainty
Original conceptual SVG · scalableIllustrative effect sizes and confidence intervals, not research data. A reference line marks the null value in this abstract example.
Read an interval
A 95% frequentist confidence interval is built by a procedure that covers the fixed true parameter in 95% of repeated samples under its assumptions; it is not a 95% posterior probability for a specific interval.
Read a p-value
A p-value is not the probability that the null hypothesis is true, nor the probability the study result happened by chance.
Go beyond thresholds
Consider effect size, precision, multiplicity, study design, confounding, missing data and practical significance alongside the statistical result.
Reference and next reading
Explore the original curriculum and publisher-hosted resources for full-depth reading; this note is an original schematic introduction, not an exhaustive chapter.