1. Examine the power curves. There are three curves, one for the 0.01, one for the 0.05, and one for the 0.10 significance level. The X axis shows sample size, the Y axis shows power. Note the effect of sample size and significance level on power.

  2. The default difference between the population mean and hypothesized mean is 1.55. Use the slider to change this value and note the effect on the power curves.

  3. Change the population standard deviation (sd) and notice its effect on power.

  4. Compare the power of one-tailed and two-tailed tests when the difference between the population mean and hypothesized mean is 2. Determine which is higher.

  5. Set the difference between the population mean and hypothesized mean to zero. Since the null hypothetsis is true, the Y axis no shows the Type I error rate, not power. Note the effect of sample size on the Type I error rate.

  6. Determine the effect of changing the standard deviation on the Type I error rate.