A mathematical quantity that indicates the probability a study has of obtaining a statistically significant effect. A high power of 80 percent, or 0.8, indicates that the study - if conducted repeatedly - would produce a statistically significant effect 80 percent of the time. On the other hand, a power of only 0.1 means there would be a 90 percent chance that the research missed the effect - if one exists at all.
The power of a statistical test is the probability that the test will reject a false null hypothesis, or in other words that it will not make a Type II error. As power increases, the chances of a Type II error decrease, and vice versa. The probability of a Type II error is referred to as Î².