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I'd like to thank everyone on the forum because the information I gain on the forum has been VERY helpful.[/FONT]

[FONT="]As many other users I got confused between d2 and d2* because of misleading statements on MSA'th edition and the change in their methods (constants, d2 usage with small group sizes etc) with the earlier editions.

This is my first post (I believe) and I wanted to explain d2 vs d2* in my perception.[/FONT]

[FONT="]In GRR, We calculate all R_bar in one or another way to determine the variation and, [/FONT]

[FONT="]m= Length of the Range equation that is used [/FONT]

[FONT="]R=(Max x(1),?.x(m))- (Min x(1),?.x(m)))[/FONT]

[FONT="]g=How many unique range calculations do we have for the final R_bar value[/FONT]

[FONT="]g= In R_bar= average (R(1)+...+R(g)) [/FONT]

[FONT="] In a O (3 Operator) x T( 3 trials) x P (10 parts ) Gage R&R study (Prepare your own excel GRR Sheet for a better understanding. It takes 2 hours for a beginner but then you may have a solid understanding)[/FONT]

[FONT="]Repeatability is calculated by first with a range operation for each individual reading set (Trial 1 thru Trial 3 so our Range equation length is 3[/FONT]

[FONT="]Reproducibility is based on the average reading (of all parts and trials) of each operator. Our range equation is [/FONT]

[FONT="]R=Max [ X_BAR_ (OP1) ,X_BAR_ (OP2) , X_BAR_ (OP2) ]- MIN [ X_BAR_ (OP1) ,X_BAR_ (OP2) , X_BAR_ (OP2) ][/FONT]

[FONT="]So m=3 since the length of R is 3 in this example. [/FONT]

[FONT="]g=1 since we only have ?1? unique R equation. [/FONT]

[FONT="](There is a further deduction step due to contamination coming from repeatability but that is not the subject of this topic)[/FONT]

[FONT="]Part to Part variation is calculated by comparing the average of all readings for each individual part [/FONT]

[FONT="]R=Max [ X_BAR_ (PART1) ,X_BAR_ (PART2) ,?, X_BAR_ (PART10) ]- [/FONT]

[FONT="]MIN [ X_BAR_ (PART1) ,X_BAR_ (PART2) ,?, X_BAR_ (PART10 ][/FONT]

[FONT="]So m=10 since the length of R is 10 in this example. [/FONT]

[FONT="]g=1 since we only have ?1? unique R equation.

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[FONT="]I hope it's been helpful.

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