Analysis is conducted with simulated subjects drawn from the virtual population. Resampling procedures will be discussed in another section. Last but not least, low power does not necessarily make your study a poor one if you found a significant difference. Yes, even if the null is rejected, the power may still be low. But this can be interpreted as a strength rather than as a weakness.
Power is the probability of detecting a true difference.
If I don't have adequate power, I may not find a significant result. Download the compressed program. The archive should be decompressed by your web browser. Choose Power Simulation from the popup menu. Manipulate effect size , sample size , and alpha level on the left.