Select Use test and confdience intervals based on normal distribution to display results for the test based on the normal distribution, also called the F-test. The results for the F-test are displayed if you enter summary data for the size and variance (or standard deviation) for each sample. With the F-test, results for Bonett's method or Levene's method are not displayed.
The F-test is accurate only for normally distributed data. Even small departures from normality can cause the F-test to be inaccurate, even with large samples. However, if the data conform to the normal distribution, then the F-test is typically more powerful than either Bonett's method or Levene's method.