Learn about U Chart

What is U chart?

A u-chart happens to be an attributes control chart which uses the data that is collected in subgroups of different sizes. These U-charts tells us how the how the process, i.e. measured by the number of nonconformities per item or group of items, changes during a period of time. In this case the nonconformities are defects that are usually found in the subgroup taken as a sample. These nonconformities can also be described as any attributes that is present but it should not be present, or any attributes that is not present but should have been present. Some examples of nonconformities are a blemish, scratch; missing button, bubble,   dent, and a tear. U-charts are also used to determine whether or note the process is stable and predictable, and they also help the organization in monitoring the new improvement practices that are implemented.

Some of the software that you can use to create U Charts is:

• SQCpack
• CHARTrunner

Scenarios when you make use of U charts:

• U charts can be used in scenarios when the item is too complex to be ruled out as too simple conformities or nonconformities.
• When you need to judge the stability of the system you are using.
• When the data is the count of nonconformities per sub group
• When the counts need to be converted to proportions
• When the possible nonconformities are been identified before the data is collected.
• When the time order of sub groups preserved

You can also make use of U charts to determine how the process is running, here you calculate the way the process was working in the past and then compare how it is running now. When you get a good understanding of the way the process is going on, then you will be able to further improve your process in a better manner.

Why are control charts important?

Control charts are important because, without the control chart you cannot determine how the process is going. The control chart will help you keep track of your process and if you have stopped collecting data can only have your opinion to know whether the process is going smoothly or not.