# Control Chart Types - How do I Choose the Right One?

## What's the difference between variable and attribute control charts?

#### If you are struggling with these questions, you are not alone.

You can take classes, read articles or find a good decision tree, but next week, you won't remember what you learned...

### There are two main categories of control charts:

1. Variable control charts for measured data.
2. Attribute control charts for counted data.

Within these two categories there are seven standard types of control charts. These are often refered to as Shewhart control charts because they were invented by Walter A. Shewhart who worked for Bell Labs in the 1920s.

### QI Macros can analyze your data and choose the correct Shewhart control chart for you

Shewhart Variable Control Charts

#### Use for Measured Data

time, money, length, width, depth, weight, etc.
Often contains decimals (.006, 8.9, 74.05)

Shewhart Attribute Control Charts

#### Use for Counted Data

number of defects, errors or defective items
Always a whole number (1, 44, 75)

### Why are there so many types of control charts? What makes them different?

#### Each control chart uses a different formula to account for three characteristics of the underlying data:

1. The type of data (measured or counted)
2. How measurements are grouped or what is counted
3. The sample size

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- National Association of Healthcare Quality Conference

### QI Macros Draws These Specialized Control Charts Too

Other Variable Control Charts
Other Attribute Control Charts

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