Formula for D2 constant

Jeez, can these questions get any easier???  Try this on for size and take it from here:
Tables for d2 factors run from samples of 2 to over 100 (reference Statistical Quality Control, seventh edition, Grant and Leavenworth, ISBN 0-07-024162-7, Table C, page 717).I do not know the derivation of the d2 factor however it is the expected value of R bar divided by sigma of the universe at different sample sizes. For a discussion of the d2 factor see the text mentioned above or Quality Control and Industrial Statistics By Acheson J. Duncan. My edition is pretty old but I am sure it is discussed in newer revisions of the text.

Hello Bower. Thanks I hope this is right.  I know I saw this somewhere before but could not find it.
I did a regression and came up with this formula, where x is the sample size: .3x  -.037x^2 + .0003x^3 – .0000017x^4 + 3.1 log(x)
It is accurate to within .04 for all values of x, and the worst cases are the small sample sizes.
I wish I could find that fornmula again.

Darth, I tried a linear regression, and I had high r^2. But I looked at a scatter plot and saw that is was a log function. I had to play a little with the factors, sort of trade them off to get the answer I had. Take a look at your residuals, you will find taht some of the data points are quite a bit off. Probably the low numbers.  A regression has the best fit in the middle of the range.

When Darth is showing up,Stan disappears

HB, how do you import a photo?

You don’t, they just sneak across the border when the sun goes down.

Thanks Bower,
I just couldn’t find the formula anywhere. Where would we be without guys like Tippett and Duncan–not the most recognized names, but certainly pillars of today’s quality control.

Not a problem, my pleasure. I have sent it to the address provided so please be on the lookout for it. You won’t be disappointed.

Shaun, my spreadsheet is for illustrative purposes and does not have the ability for handling large samples.  Another poster indicated he had one for large samples.  Possibly he will read this and respond to you.

Can anyone provide an Excel Shhet with D2 valuse in for subgroups of n=2 TO n=100

Hi LeeIf you post an e-mail address I’ll send you a copy of my spreadsheet.Best WishesBower Chiel

Can I also get the spreadsheet? I am desperately looking for formula for d2 as I need to find the relation between Cpk and Ppk (or/and Cp vs. Pp).  As the difference is only standard deviation I assume that d2 factor was calculated based on z-shift assumption of 1.5 – do I get it right?
Thanks,

Please send d2 formula to my email address:
[email protected]!

Cp and Pp (or Cpk and Ppk) are relates by formula only.
Recall that Cp = (USL-LSL)/(6*std. dev) and Ppk is given by min(((x-LSL)/(3*Std. dev)), (ULS-x)/(3*Std. Dev)).
For the Cp and Cpk, the value for Std. Dev is given by MR/d2  This is getting an estimation of the Std. dev using the part to part range.
The Pp and Ppk uses the overall standard deviation (from excel, this would be like using the =STDEV( ) formula) to estimate the long term standard deviation.
From my learnings, there is no other relationship, maybe someone else can shine a brighter light on this…?

It very simple.  Use six sigma table to calcluate sigma and this make it easy to draw control chart.

Hi GordonPost an e-mail address and I’ll happily send you, or anyone else who is interested, a copy of my Excel spreadsheet that calculates the value of d2 for any sample size you enter.Best WishesBower Chiel

could you send me a copy of that D2 spreadsheet too?  appraciate it!

Hi Need
Post an e-mail address and I’ll send you the spreadsheet.
Bower Chiel

Hi DenisI’ve sent the spreadsheet that computes d2. I’ve also sent a table of values of both d2 and d3 for n =2 up to n = 100 that I’ve created with the help of a mathematician at Edinburgh Napier University. This table also includes corresponding values of d2* for 1 to 20 subgroups. I’ll happily send both to anyone posting an e-mail address.Best WishesBower Chiel

Dear Bower Chiel
I have great interest to know your an Excel spreadsheet that calculates d2 for n=2 to n=100. If you think it is  possible to send me a copy I’ll apreciate for sure.
Bes Regards,

Thank You Bower for your promptly response. This is my e-address:
[email protected] 

dear Bowel Chiel,
Please send me the table also. My e-mail address is [email protected]
Thanks and best regards,
Nuke

BC:I have calculated the table values for normal and non-normal distributions for n=2-50. Could you send your spreadsheet so I could compare the results?6sigmaguru(at)gmail(dot)comCheers, Alastair

Hi Bower,I am very interested to know how d2 is calculated for n=2 to n=100.
I would highly appreciate if you could email me a copy of the Excel file you have.
My email is ab.ssbb at gmail.comThanks

Hello Bower Chiel:  I would appreciate a copy of the spreadsheet that computes d2.  [email protected]

I’d like a copy of the spreadsheet too.  ealanni(at)windstream(dot)net.
Now a question:  To keep life simple on the production floor, I almost always (40 or 50 instances) have a sample size of 5.  In one or two instances a sample size of 10.   Because of the desire to keep the sample size small enough to keep things simple I do not need D2 values beyond what any readily availble source provides.  So, my question is this: What causes the need for the sample sizes of >100 and abandoning simplicity/speed of analysis on the plant floor?
 

Hi Bower,
Could you please send me copy of the d2 spreadsheet?
Thank you in advance.
Email: [email protected]
Kind Regards,
karishma

Hallo Bower Chiel,
Thanks please send me the excell sheet for D2. I will also like to know How this Emperical relation deviced for Rbar / d2 = std deviation.
My email Adress is [email protected]
Regards
Pradeep
 

Hi Dear Bower Chiel,
I am interested in D2 values for N2….N100
My email address is [email protected] or [email protected]
Please mail.
Regards
Pradeep

Hi Bower,
could you send your D2 spreadheet on email [email protected]
Thank you in advance
Best David

Let’s see, if I want to get a message to Bower I’m going to post a reply to a posting by… Skala, yea, that’ll do it.
I heard that they can’t send this via e-mail.  Please tie a red bandana around your mailbox and they’ll print out a copy and drop it off.

I would be grateful if somebody could send me an excel copy of the d2 constants. [email protected]  Many thanks