Statistical power is the probability of rejecting a false null hypothesis. When we test hypotheses, we always test the null hypothesis against an alternative/research hypothesis. We are in an odd position; we want to reject our null hypothesis in favor of the alternative.

Why Is This Important?

As researchers, we put a lot of effort into designing and conducting our research. This effort may be wasted if we do not have sufficient power in our studies to find the effect of interest.

Before we learn about statistical power as a probability, let's review the process of testing hypotheses and the concept of error.