Enter your data for Power and Sample Size for 1 Variance

Stat > Power and Sample Size > 1 Variance

Complete the following steps to specify the data for the power and sample size calculation.

1. From the drop-down list, select whether you want to analyze a ratio of standard deviations or a ratio of variances.
2. Specify values for two of the following power function variables. Leave the variable that you want to calculate blank.
• Sample sizes: Enter a sample size of interest. To assess the effect of different sample sizes, enter multiple values. Larger sample sizes give the test more power to detect a difference.
Tip

If you enter multiple values into a field, separate the values with a space. You can also use shorthand notation to indicate multiple values. For example, you can enter 10:40/5 to indicate sample sizes from 10 to 40 in increments of 5.

• Ratios: Enter one or more values to specify the difference that you want to detect between a standard deviation or variance and a hypothesized standard deviation or variance (target value). Usually, you enter the smallest ratio that has practical consequences for your application. A ratio close to 1 suggests equality between the two standard deviations or variances.

• Power values: Enter one or more values to specify the probability that the test detects a difference between the two variances or standard deviations when a difference actually exists. Common values are 0.8 and 0.9. For example, analysts enter 0.9 because they want a 90% chance that the test will detect an important difference between the standard deviation of the width of dowels and the target standard deviation (hypothesized standard deviation) when a difference actually exists.
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