Select the option that best describes your data.

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 Subgroup
size, enter a column that identifies the subgroup for each measurement or enter a number that indicates the subgroup size. To perform a between/within analysis, you must have at least 2 observations in at least one subgroup. Enter a number for subgroups of the same size. For example, if each subgroup contains measurements for five items, enter 5. If you enter a column of subgroup IDs, the subgroup sizes do not need to be equal.
###### Note

Observations within each subgroup should be in adjacent rows of the worksheet. For more information on using columns to define subgroups, go to Using subgroups to assess process capability.

In this worksheet, the Diameter column contains the diameters of the piston rings. The Subgroup ID column identifies the subgroup for each measurement.

C1 | C2 |
---|---|

Diameter | Subgroup ID |

74.030 | 1 |

74.002 | 1 |

74.019 | 1 |

73.992 | 1 |

73.995 | 2 |

73.992 | 2 |

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

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 of the worksheet contains the diameters of the piston rings in subgroup 1. The second row of the worksheet 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 |

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.

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.

If you know the historical mean or the historical standard deviations of your process, or if you have estimates obtained from past data, enter the values for the analysis.

- Historical mean
- Enter a value for the mean of the population distribution.
- Historical Standard Deviations
- Enter values for the historical standard deviations.
- Within subgroup
- Enter a value for the standard deviation within subgroups of the population distribution.
- Between subgroups
- Enter a value for the standard deviation between subgroups of the population distribution.

If you do not enter historical population parameters, Minitab estimates the mean and standard deviations from your sample data and uses those estimates to calculate process capability.

If you want to specify the method that Minitab uses to estimate the standard deviation from your sample data, click Estimate.