Talk:Shewhart individuals control chart

Page title punctuation seems odd to me!
Shouldn't the title rather be Individuals' moving-range chart? A single apostrophe after the s to indicate the plural possessive. I don't see why there should be a forward slash in the title at all. DFH 07:17, 9 August 2007 (UTC)

Stub
This article appears to be a stub, could somebody please mark it as such? And add content to it? A picture would be helpful. 216.254.190.174 (talk) 14:34, 10 June 2009 (UTC)

Done. Tom Hopper 15:52, 19 January 2010 (UTC)

Basis of Charts and Data Normalcy
The statement that the XmR (a.k.a. ImR) charts are based on an assumption of data normalcy is incorrect, as are the following three bullet points.

Shewhart himself goes to some length on this subject. I have a note here that he wrote


 * Some of the earliest attempts to characterize a state of statistical control were inspired by the belief that there existed a special form of frequency function f and it was early argued that the normal law characterized such a state. When the normal law was found to be inadequate, then generalized f

Tom Hopper 15:46, 19 January 2010 (UTC) —Preceding unsigned comment added by Thopper (talk • contribs)

Notes and References
Anyone with the 2004 edition of Montgomery, please help clean up the sources by checking where values for $D4$ and $d2$ are given in that edition (in the 1996 edition, it's the table in appendix A-15). Then update the &lt;ref name ="Montgomery1996" /&gt; to &lt;ref name ="Montgomery2004" /&gt;, update &#123;&#123;rp|num&#125;&#125; references and eliminate the citation of Montgomery 1996.

Tom Hopper 09:20, 9 February 2010 (UTC)
 * Mission Accomplished. I've also changed the text ("The value 2.66 is obtained by multiplying dividing 3 by the $d2$ statistic for $n=2$") to match $$\overline{x} \pm 3\frac {\overline{MR}}{d_2}$$ from http://www.itl.nist.gov/div898/handbook/pmc/section3/pmc322.htm (and from Montgomery).  -- DanielPenfield (talk) 20:43, 9 February 2010 (UTC)

The normal distribution is assumed in the calculation of control limits?
"The normal distribution is assumed in the calculation of control limits."

What is the basis for this statement? I thought that, in fact, what makes this particular control chart (Indx/Mr) robust is that a NORMAL distribution is NOT assumed or required. 69.250.187.206 (talk) —Preceding undated comment added 12:45, 5 December 2011 (UTC).

Did any body actually read Wheeler, FOOTNOTE 6 shows that normal iS NOT assumed or required? 69.250.187.206 (talk) —Preceding undated comment added 13:01, 5 December 2011 (UTC).

Correct Attribution
Per Donald Wheeler, the Individuals control chart was first proposed in 1942 by W. J. Jennett as cited in a 1953 article by Joan Keen and Denys J. Page in the journal Applied Statistics. 205.175.240.242 (talk) 12:07, 20 April 2016 (UTC)Alan Miner

Normality and Indiv/MR charts
The chart may be quite robust to non-normality, but it seems more than odd to say that the chart does _not_ assume normality immediately before the (accurate) statement that the limit for the moving range chart arises directly from the normal distribution. Similarly, D4 and so on all arise (directly or otherwise) from an underlying normal distribution for the data from which the mean range etc are calculated. SHewhart (iirc) relaxed the normality assumption by picking 2 and 3 sd for limits, but the underlying calculations clearly do assume normality. — Preceding unsigned comment added by Slrellison (talk • contribs) 10:55, 20 March 2017 (UTC)