p Chart in Excel

Use a p chart When Counting the Fraction Defective

The p chart is used to evaluate process stability when counting defective items and when the sample size varies (e.g. the total number of circuit boards, meals, or bills delivered varies from one sampling period to the next.)

Defects (u charts) vs Defective Items (p charts):
  • Defects - each item in a sample can have more than one defect (e.g. scratches on a car door, errors on a bill, missing products in a shipment).
  • Defective items: Each item is only counted once (e.g car doors that need to be repainted, bills that are wrong, incomplete shipments, C-sections in a delivery),

p chart data looks like this:

p chart data in Excel

To create a p chart in Excel using QI Macros:

  1. Just click and drag over the data to select it.
  2. Then click on the QI Macros menu, Control Charts, then p chart.
  3. QI Macros will all of the math and draw the p chart for you. QI Macros will also turn any unstable points or conditions on the p chart red. These should be investigated.

Example of a p chart Created using QI Macros for Excel.

The stair step or skyline control limits are the result of the varying sample sizes.

p chart in Excel created with the QI Macros software

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To create a P Chart using QI Macros...
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