Statistical power calculators
The power calculator computes the test power based on the sample size and draw an accurate power analysis chart.
Larger sample size increases the statistical power.
Researchers usually use the power of 0.8 which mean the probability of type II error (β), failure to reject an incorrect H0.2, is 0.2. The commonly used significant level (α) is 0.05. β is usually four times bigger than α, since rejecting a correct null assumption consider to be more severe than failing to reject a correct invalid assumption.