Should I use the chi-square method or the Bonett method for 1 variance test?

Minitab uses two methods of calculating a confidence interval for the standard deviation and variance: the chi-square method and the Bonett method. Use these guidelines to determine which method to use:
  • If your sample data come from a normally distributed population, use the chi-square method. However, this method will produce inaccurate results if your sample does not come from an approximately normal population.
  • The Bonett method is robust against departures from normality. If your data are strongly nonnormal, the Bonett method is significantly more accurate than the chi-square method. Minitab cannot calculate the Bonett method with summarized data.
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