Power & Error VisualizerStatLens

H₀ (Null) H₁ (Alternative) α (Type I Error) β (Type II Error) Power (1 − β)
Power (1 − β)
0.8413
Type II Error (β)
0.1587
Type I Error (α)
0.0500
Critical value
1.6449

Power & Error Visualizer

Explore how discernibility level (α), sample size (n), effect size (δ), and population variability (σ) interact to determine statistical power.

A note on wording: α is the discernibility level here, following the course text. Many books and exercise sets call the same number the significance level — they mean the same thing.

What am I looking at?

Two overlapping normal distributions represent the sampling distribution of the sample mean under:

The standard error of each distribution is σ / √n. Increasing n makes both curves narrower.

Shaded regions

Key relationships

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