K
The formulas use 5.15, which reprsents the number of standard deviations that contain the central 99% of the normal distribution.
The only way to make a realistic statement regarding the %-contribution of the variation is to obtain variance components using the ANOVA-method (these are the variances as opposed to the std. deviations). The variances can be added to calculate percentages of the total observed variation. By dividing the R&R variance by the sum of ALL the variances you can determine the %-contribution of the measurement system.
That is one reason I like MINITAB better than JMP. MINITAB provides both the average & range and ANOVA methods. I prefer the ANOVA method. JMP can do the ANOVA method, but more handwork needs to be done.
I used to have the demo for StatGraphics 5, but it has expired and I can't remember much about its GR&R tool.
I tend to like MINITAB because overall it has a better laid out set of tools. With respect to the GR&R, StatGraphic's latest version added a one-page report much like MINITAB has had for several years, but I still like MINITAB's better.
Ken K.
The only way to make a realistic statement regarding the %-contribution of the variation is to obtain variance components using the ANOVA-method (these are the variances as opposed to the std. deviations). The variances can be added to calculate percentages of the total observed variation. By dividing the R&R variance by the sum of ALL the variances you can determine the %-contribution of the measurement system.
That is one reason I like MINITAB better than JMP. MINITAB provides both the average & range and ANOVA methods. I prefer the ANOVA method. JMP can do the ANOVA method, but more handwork needs to be done.
I used to have the demo for StatGraphics 5, but it has expired and I can't remember much about its GR&R tool.
I tend to like MINITAB because overall it has a better laid out set of tools. With respect to the GR&R, StatGraphic's latest version added a one-page report much like MINITAB has had for several years, but I still like MINITAB's better.
Ken K.