statistical power

The power of a statistical test is the probability that the test will reject a false null hypothesis (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 β. Therefore power is equal to 1 − β.
See more at Wikipedia.org...

The probability of rejecting a false statistical null hypothesis.
For more information see the chapter on Power Analysis .