Normal Probability Plot Chart

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The SPC software tool to answer the question “Can we meet our target?”

The GainSeeker® Normal Probability Plot Chart gives you a useful visual representation of data to help you assess whether the data are normally distributed.  If they are normally distributed, they will be plotted close to the diagonal line as shown below:

Normal Probability Plot

Normal Probability Plot

You’ll answer the question: “Can we meet our target?”

Other types of distribution have different curve characteristics.  For example, left skewed data will plot by bending downward and to the right of the diagonal line, like this:

Normal Probability Plot - Skewed Data

Normal Probability Plot – Skewed Data

The Normal Probability Plot also gives you an easy-to-see visual answer to the question, “Can we meet our target?”  You can get this information by displaying specifications on the chart, and then looking at where the diagonal line crosses those specifications.  You can see that by looking at the horizontal red lines on the chart below:

Normal Probability Plot - Can we meet targets?

Normal Probability Plot – Can we meet targets?

For manufacturing and non-manufacturing applications too.

This example is telling us that you are below specification about 10% of the time.  It also says that you are above specification about 10% of the time.  If this data is coming from a stable control chart, you can predict that as long as the process doesn’t change, you will continue to produce those same results.

This tool can also be used for non-manufacturing applications.  Closing calls in a call center, sales targets and results, or net income could all be valid ways to use this chart.  The Normal Probability Plot on a Key Performance Indicator Dashboard of key business metrics can be a powerful tool you’ll use.

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