Statistical Power

Statistical Power

Statistical power is the probability of detecting a true effect in your sample when it actually exists in the population (i.e., identifying a true positive).

A study with low power may fail to find significance even when a real effect is present, leading you to incorrectly conclude that no effect exists.
Understanding statistical power helps you design experiments that are both reliable and reproducible.

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Why It Matters

Statistical power can help you answer key design questions:

• What is the chance my results will replicate if someone else repeats my experiment?
• How many subjects or samples should I include in my study?

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Helpful Tools

You can easily estimate power using web-based tools and Python packages:

• Russ Lenth’s Power and Sample Size Applets – simple, interactive calculators
• Statistics Kingdom Power Calculators – accessible web tools for common tests
• Pingouin Stats Package – Python library with built-in power calculators for tests like t-tests and ANOVAs

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Learn More

Check out Lex’s Lecture on Power Analyses!