np Chart Formulas

The np chart is used to evaluate process stability when counting the number or fraction defective.

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 100 or errors per each sample of 50 invoices.

Here is the formula used to calculate a np chart.

np chart formula

Conforms with ANSI/ASQC B1, B2, B3 1996

Learn More...

The np chart is just one of the tools included in the QI Macros for Excel SPC Software for Excel.


Why Choose QI Macros Over Other Control Chart Software?

affordable

Affordable

  • Only $279 USD - less with quantity discounts
  • No annual subscription fees
  • Free technical support

easy to use

Easy to Use

  • Works right in Excel
  • Create a chart in seconds
  • Easy to customize & share charts

proven and trusted

Proven and Trusted

  • More than 100,000 users
  • In More than 80 countries
  • Five Star CNET Rating - Virus free