Statistical Applets Statistical Power

This applet illustrates the power of statistical tests. Finding the power of a test assumes that you have set a fixed significance level α for the test. Review the "Statistical Significance" applet to recall how tests with significance level α work. The top curve shows the sampling distribution of the sample mean x when your null hypothesis is true. The yellow area under this curve is α, the probability of rejecting H₀ when it is really true. The bottom curve shows the sampling distribution of x when your chosen alternative is true. The red area under this curve is the power, the probability of rejecting H₀ when the alternative is really true.	To set up the test, enter your information: What null hypothesis H₀ about the mean μ do you want to test? Is your alternative hypothesis one-sided high, one-sided low, or two-sided? What level of significance α do you require? How many observations do you have? What is the known value of the standard deviation σ? Finally, against what specific alternative value of the mean μ do you want to find the power? When you have entered your information, click UPDATE.

Statistical Applets

Statistical Power

This applet illustrates the power of statistical tests. Finding the power of a test assumes that you have set a fixed significance level α for the test. Review the "Statistical Significance" applet to recall how tests with significance level α work.

The top curve shows the sampling distribution of the sample mean x when your null hypothesis is true. The yellow area under this curve is α, the probability of rejecting H₀ when it is really true. The bottom curve shows the sampling distribution of x when your chosen alternative is true. The red area under this curve is the power, the probability of rejecting H₀ when the alternative is really true.

To set up the test, enter your information: What null hypothesis H₀ about the mean μ do you want to test? Is your alternative hypothesis one-sided high, one-sided low, or two-sided? What level of significance α do you require? How many observations do you have? What is the known value of the standard deviation σ? Finally, against what specific alternative value of the mean μ do you want to find the power? When you have entered your information, click UPDATE.