# Don't understand why there are so many types of control charts?

## Go Deeper

### The two main categories of control charts are variable and attribute:

1. Variable control charts for measured data (most often decimals, e.g., 3.24).
2. Attribute control charts for counted data (most often integers, e.g., 1, 2, 3).

Within these two categories there are seven standard types of control charts. These are often referred 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

### QI Macros Add-in for Excel:

Installs a new tab on your Excel menu. You don't need to learn a new application.

Will make the calculations for you. You don't need to learn any formulas.

Will analyze your data and select the right chart for you. You don't need to memorize rules or get lost in a forest of decision trees.

It is so simple to use and anybody can use it. It's like a magic program.

You input the data, you click the button and, "poof," there it is!
It's all done for you. It's great, I love it...

- National Association of Healthcare Quality Conference

### QI Macros Also Draws These Specialized Control Charts

Other Variable Control Charts
Other Attribute Control Charts