A Review of Statistical Power Analysis Software

Although ecologists have become increasingly sophisticated in applying tests for statistical significance, few are aware of the power of these tests. Statistical power is the probability of getting a statistically significant result given that there is a biologically real effect in the population being studied. If a particular test is not statistically significant, is it because there is no effect or because the study design makes it unlikely that a biologically real effect would be detected? Power analysis can distinguish between these alternatives, and is therefore a critical component of designing experiments and testing results (Toft and Shea 1983, Rotenberry and Weins 1985, Peterman 1990, Fairweather 1991, Taylor and Gerrodette 1993, Thomas and Juanes 1996).