Significance Level (α)
Pre-set risk threshold for wrongly rejecting H₀ — usually α = 0.05.
Also known as: alpha, α, significance threshold
The significance level α sets how much Type I error risk is accepted — the probability of rejecting H₀ when it is actually true ("false alarm").
- α = 0.05 — standard in industry and research; 5 % false-alarm rate per test
- α = 0.01 — for critical decisions (safety, approvals)
- α = 0.001 — very strict, e.g. under millions of parallel tests (genome studies)
See also
Used in
In the Algorithm Lab
Sources
- Neyman, J. & Pearson, E. S. — On the Problem of the Most Efficient Tests, 1933
- Wasserstein, R. L. & Lazar, N. A. — The ASA Statement on p-Values, 2016