Control Chart Selection
The following table can guide you to select the control chart to use depending on the type of data, what you want to track and sample size.
Data | Type | Tracking | Sample | Charts |
Variable Data | Individuals | Process level (individuals) | Subgroup size = 1, data point >30 | I Chart |
Process variation (moving range) | Subgroup size = 1, data point >30 | MR Chart | ||
Process level and variation | Subgroup size = 1, data point >30 | I-MR Chart | ||
Subgroups | Process level (means) | 5-10 subgroups | Xbar Chart | |
Process variation (ranges) | 5-10 subgroups, small subgroups (<= 5) | R Chart | ||
Process variation (standard deviations) | 5-10 subgroups, large subgroups (<= 5) | S Chart | ||
Process level and variation | 5-10 subgroups, small subgroups (<= 5) | XBar-R Chart | ||
Process level and variation | 5-10 subgroups, large subgroups (<= 5) | XBar-S Chart | ||
Process level and variation | 5-10 subgroups, large subgroups (<= 5) | I-MR-R/S Chart | ||
Non-weighted | Process level (Minor shifts) | Subgroups >= 1, large samples | MA Chart | |
Weighted | Process level (Minor shifts) | Subgroups >= 1, large samples | EWMA Chart | |
Attribute Data | Defectives (Defective product) | Number of defectives | Equal subgroup size | NP Chart |
Percentage of defectives | Different (or same) subgroup size | P Chart | ||
Defects (Product can have more than one defect) | Number of defects | Equal subgroup size | C Chart | |
Number defects per unit | Different (or same) subgroup size | U Chart |