Use to determine the sample size that is required to achieve a specific margin of error for a tolerance interval. Conversely, you can calculate the margin of error based on sample size.

Minitab shows results for both the normal and nonparametric methods.

You manufacture round metal washers. You want to assess the variability in the thickness of your washers. You plan to measure a sample of washers and to calculate a tolerance interval that includes 95% of the population.

If your sample size is small, then the margin of error may be too large and the tolerance interval may greatly overestimate the variability in the thickness of your washers. You want to know how many washers you need to measure to achieve margins of error of 1% and 2% for the tolerance interval. You also want to know what margins of error you can achieve with samples of 50 or 100 washers.