# Enter your data for Tolerance Intervals (Nonnormal Distribution)

Stat > Quality Tools > Tolerance Intervals (Nonnormal Distribution)

Complete the following steps to specify the data for your analysis.

1. In Variables, enter the columns that contain the sample data. Minitab performs separate tolerance interval analyses on each column that you enter.
2. From Distribution, select the distribution that the data follow. For more information on a distribution, go to Distributions for Tolerance Intervals (Nonnormal distribution).
• Lognormal - Use when the logarithm of the random variable is normally distributed.
• Gamma - Use to model positive data values that are skewed to the right.
• Exponential - Use to model the time between events in a homogeneous Poisson process.
• Smallest extreme value - Use to model data values that are skewed to the left. The smallest extreme value distribution is the distribution of the minimum of a large number of random variables from a specific group of distributions. It's often used to model the logarithm of failure times.
• Weibull - Usually used to describe failure distributions. It can also be used to model the minimum of a large number of positive random variables from a specific group of distributions.
• Largest extreme value - Use to model data values that are skewed to the right. It's usually used to describe the maximum of a large number of random variables from a specific group of distributions.
• Logistic - Use to model distributions that have a similar shape to the normal distribution, but with longer tails.
• Loglogistic - Use when the logarithm of the variable is logistically distributed.
• Assume none - Use when you are not willing to make any assumption about the population of your data. Minitab only displays results for the nonparametric method. However, a large sample is usually required for the result to be accurate.
3. In Minimum percentage of population in interval, enter the minimum percentage of the population that you want a two-sided tolerance interval to include, or a one-sided lower limit to be less than or a one-sided upper limit to be greater than.
In this worksheet, Brightness contains the sample data.
C1
Brightness
81.50
78.80
79.55
83.02
80.26
86.50
84.76
76.74
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