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I-MR-R/S (Between/Within) ChartSummary |
Use I-MR-R/S (Between/Within) chart to create a control chart that uses both between-subgroup and within-subgroup variation. For example, a process for coating paper with a thin film may have both between-subgroup and within-subgroup variation. The within-subgroup variation is the variation is film thickness within one roll (subgroup). If the machine is reset for each roll, then there might be variation between rolls (subgroups).
The I-MR-R/S chart consists of the following:
Note |
Whether Minitab displays an R chart or an S chart depends on the size of the subgroups. If more than 50% of the subgroups are the same size, then the most common subgroup size determines the chart. Otherwise, the largest subgroup size determines the chart. If the subgroup size is 8 or less, Minitab displays an R chart. If the subgroup size is 9 or more, Minitab displays an S chart. |
The combination of the three charts provides a method of assessing the stability of process location, the between-subgroup component of variation, and the within-subgroup component of variation.
Data Description |
An injection-molding company uses a die to create parts. Each die produces five parts at one time. Twenty subgroups of five parts each were collected.
Data: InjectionMolding.MTW (available in the Sample Data folder).