Enter your data for Nonnormal Capability Analysis

Stat > Quality Tools > Capability Analysis > Nonnormal

In This Topic

Enter your data
Fit distribution
Specification limits

Enter your data

Select the option that best describes your data.

Single column

If your data are in a single column of the worksheet, complete the following steps.

Under Data are arranged as, select Single column.
In Single column, enter the column of numeric data that you want to analyze.

In this worksheet, Diameter contains the diameter of piston rings.

C1
Diameter
74.030
74.002
74.019
73.992
73.995

Subgroups across rows of

If you have subgroups arranged in rows across several columns of the worksheet, and each row represents a single subgroup, complete the following steps.

Note

If you use this option to enter your data, all subgroups must be the same size. If your subgroups are arranged in rows and the sizes differ, you can enter a missing value symbol "*" in worksheet cells as needed to make all the subgroup sizes the same.

Under Data are arranged as, select Subgroups across rows of.
In Subgroups across rows of, enter the columns of numeric data that you want to analyze.

In this worksheet, the first row contains the diameters of the piston rings in subgroup 1. The second row contains the diameters of the piston rings in subgroup 2, and so on.

C1	C2	C3
Observation 1	Observation 2	Observation 3
74.030	73.995	73.988
74.002	73.992	74.024
74.019	74.011	74.021
73.992	74.004	74.005

Fit distribution

From the drop-down list, select a nonnormal distribution to fit your data. To produce a reliable estimate of process capability, the data must follow the distribution that you select. If you are unsure which distribution best fits your data, use Individual Distribution Identification.

For more information on choosing an appropriate distribution for nonnormal data, go to Capability analyses with nonnormal data.

Specification limits

To perform the analysis, you must enter a lower specification limit, an upper specification limit, or both.

Lower spec: Enter the minimum acceptable value for the product or service. If it is not possible for measurements to fall below this value, select Boundary to define the lower specification limit as a boundary.
Upper spec: Enter the maximum acceptable value for the product or service. If it is not possible for measurements to exceed this value, select Boundary to define the upper specification limit as a boundary.

Note

When you define a specification limit as a boundary, Minitab reports the expected capability indices related to the spec limit/boundary as missing values (*). Therefore, define a limit as a boundary only if it is theoretically impossible for measurements to fall beyond the limit. For example, an upper specification limit of 100% purity is a boundary because it is not possible to exceed 100% purity. A lower specification limit of 0% purity is a boundary because it is not possible to fall below 0% purity.