Talk:Np-chart

Equation should read:

$$n*pbar +/- 3*sqrt(n*pbar*(1-pbar))$$


 * Thank you, well spotted. (Note that you can sign your posts by placing four tildes.) -- Jayen 466 00:14, 6 February 2008 (UTC)

Text removed
I've removed the following text that had been added by an IP: -- Notice that the using the Central limit theorem approximation is wrong in most cases. The chance that a process will have a sample size big enough and a percentage of defects big enough in order to pass the $$n*p>5$$ approximation test is not very big. In order to calculate Control limits correctly, one must choose an α =1-P(LCL < Xi < UCL/μ=n•p) where Xi = pi•n and extract the control limits using this formula.

This does not seem to be the mainstream position on how to calculate the control limits; at the very least, it is likely to be contentious and should be backed up by a reliable source.  JN 466  23:13, 12 June 2009 (UTC)