Inference Suite
Confidence intervals for means and proportions, required sample size, and full hypothesis tests with the rejection region drawn on the curve. Covers §6.18–6.19 and §6.22.
Confidence Interval
Required Sample Size for a Mean
Test H₀: μ = μ₀
Null distribution; rejection region shaded gold, test statistic marked in red. FIG. T40-1
A 95% confidence level describes the procedure, not one interval: over many repetitions, 95% of intervals built this way capture the true parameter. And the p-value answers exactly one question — how surprising is data like ours if H₀ is true?