Re: SPC Theory question

["Carlos Mendez" <carmende@ufm.edu.gt>]

Tony Burns wrote:

>The simplest, as well as the most foolproof  approach for beginners is to
>use XmR charts instead of p, np, c or u. This takes away the need for
>decisions other than making sure the count exceeds 1. See Wheeler "Advanced
>topics in SPC" page 266.

I have noticed that when the process is stable, XmR, p, np formulas give
very similar results for the control limits. Does this make sense?

Carlos Méndez
Invenia, S.A.
invenia@guate.net
PBX - (502) 336-9669