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Create an np Chart in Excel

Use np charts when counting defective items / constant sample size

The np chart is useful when it's easy to count the number of defective items and the sample size is always the same. Examples might include: the number of defective circuit boards per 1000 or incorrect invoices per each sample of 50.

Example of np chart data

np chart data example

Example an np chart created using QI Macros

np control chart created in Excel

It's Easy to Draw a np Chart in Excel Using QI Macros

QI Macros adds a new menu to Excel and provides two ways to create charts: macros and templates

Run a Macro on Data You Have Already Collected
Select your data. Click on QI Macros > Control Charts > np chart. QI Macros does the math and draws the chart. QI Macros turns unstable points or trends turn red. These should be investigated.
Watch a np chart created by a macro

Input Data into a Fill-in-the-Blanks Template
Click on QI Macros > Control Chart Templates > np chart. Input your data into the yellow shaded area. The chart is drawn as the data is input. Run stability analysis using the chart tools menu.
Example of QI Macros np chart template

Input Data into a
Fill-in-the-Blanks Template

Click on QI Macros > Control Chart Templates > np chart.
Input your data into the yellow shaded area.
The chart is drawn as the data is input.
Run stability analysis using the chart tools menu.

Example of QI Macros np chart template

np chart template in Excel

I looked at a number of alternatives (some much more expensive than QI Macros, some in the same price range); QI Macros was head and shoulders above the competition in price/performance.

- Robert Bamford
Software Systems Quality Consulting