Control Chart Types
What's the Difference Between Variable and Attribute Control Charts?
One uses measured data; the other uses counts.
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Variable (e.g., measured time, weight, length, money, etc.)
Variable control charts use measurements (time, money, length, width, depth, weight, etc.).
When looking at data, variable measurements often have one or more decimal places (e.g., 74.05).
The most common type of variable control charts are X charts:
- XmR - Individuals and Moving Range Control Chart (especially useful in service industries)
- X bar R - Average and Range Control Chart
- X bar S - Average and Standard Deviation Control Chart
- X Median R - Median and Range Control Chart
- I-MR-R - Individuals, Moving Range (between) and Range (within) Control Chart
Less common types of variable control charts include:
- ANOM - Analysis of Means Control Chart
- Cusum - Cumulative Sum Control Chart
- EWMA - Exponentially Weighted Moving Average Control Chart
- Levey Jennings Control Chart
- Moving Average Control Chart
Attribute type control charts use counted data (number of defects, mistakes, errors, injuries, etc.)
When looking at your data, attribute data is always an integer (e.g., 1, 3, 5).
Common attribute type control charts include:
- c Control Chart
- np Control Chart
- p Control Chart (fraction defective) and q control chart
- u Control Chart (number defective)
Other attribute control charts include:
- Watch video of creating a control chart in Excel using the QI Macros
- How to use and interpret a control chart
- Control Chart examples
- How to Choose the Right Control Chart with a control chart decision tree