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

Learn here and discover the tool that will always select the right control chart for you.

There are many different types of control charts and its hard to know which control chart you should use.
You can take classes, read articles or find a good decision tree, but next week, you won't remember what you learned.
That is why we built control chart selection rules right into the code of QI Macros Control Chart Wizard. Watch it in action.

Go Deeper

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

Variable control charts for measured data (most often decimals, e.g., 3.24).
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)

Individuals Moving Range | XmR Chart: subgroup size = 1 XbarR Chart: subgroup size 2 to 5 XbarS Chart: subgroup size > 6

Shewhart Attribute Control Charts

Use for Counted Data

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

c Chart: count of defects u Chart: count of defects - varying sample size p Chart: fraction defective - varying sample size np Chart: fraction defective - constant sample size

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:

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

It sounds scary, but its not because...

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