Minitab %Tolerance ANOVA is Different than my calculations

B

Brad Gover - 2010

#1
:bonk:Hi all, I am really appriciating this web site! What I have is a print out of the %Tolerance (SV/Toler) ANOVA of 1.00. The print out for Std Dev (SD) Total Gage R&R is 0.3166. Minitab also calculates the Study Var (5.15*SD) =1.63 and the % study Var (%SV) = 1.25.

My calculation for the STD Dev Total Gage R&R is the same 0.3166.
My calculation for the Study Variation is the same 1.25%
My calculation for the P/T% is not the same 1.63%

P/T% = [(5.15*Std Dev Gage R&R)/(USL - LSL)] * 100

P/T% = [(5.15*0.3166)/(100-0)] * 100 = 1.63%

So I am thinking why the difference?:thanx:
 
Elsmar Forum Sponsor

Miner

Forum Moderator
Staff member
Admin
#2
Minitab uses 6 instead of 5.15 per the MSA 3rd edition manual. 5.15 is the 2nd edition formula.
 
B

Brad Gover - 2010

#3
:lol: Ok I figured this one out myself. Turns out when I put in the specification limits I put in the upper spec of 100 and did not enter a lower specification as that is a natural boundry. Cannot physically get less than zero. When I went back in and put the range of 100, I get a P/T% of 1.63. So now what begs the question. If you only have one sided tolerance limits should you use the range or just enter like in my case a zero for the LSL and a 100 for the USL?
:yes:
 

Miner

Forum Moderator
Staff member
Admin
#4
So now what begs the question. If you only have one sided tolerance limits should you use the range or just enter like in my case a zero for the LSL and a 100 for the USL?
:yes:
First, if you had entered 0 as a LSL and 100 as USL, you should obtain the same result as entering the range of 100. Leaving the LSL field empty was the cause of the difference.

This is how Minitab responds to a One-sided Tolerance, and is the reason for your different results. So, which method is appropriate?

This is a difficult question to answer. The AIAG MSA manual is silent on this and no other "guru" that I am aware of has spoken on it. This probably because there is no one, right answer.

Lets look a few scenarios, and I will give you my :2cents::


  • Scenario 1, Flatness: Zero is a natural boundary and there is a maximum allowable flatness specification. Presumably, there is some incentive to drive for smaller and smaller levels of flatness, thus moving farther and farther away from the USL. In this situation, you will conceivably utilize the entire tolerance spectrum. This would tend to justify what you have done. That is, using the whole range, or entering 0 as a LSL.
  • Scenario 2, Minimum Hardness: I am using the example used by Minitab in the above link. In this scenario, you are not going to strive for infinite hardness. There will be practical and economical reasons for you to "hover" a safe distance above the LSL, and to not increase over time. In this scenario, it would make more sense to use the Minitab approach. (I will casually overlook the fact that you cannot enter infinity into the USL field). The same logic could apply to a maximum activation force for a push button. If you strove for zero activation force on a conventional spring-loaded design, there would no force left to reopen the switch. In this case, the Minitab approach would also make sense.
Having said that, there will probably be 10 others that will vehemently disagree with me.:argue:
 
Thread starter Similar threads Forum Replies Date
N Tolerance Interval plots in Minitab Statistical Analysis Tools, Techniques and SPC 0
J Non-Normal Distribution Data - Tolerance Intervals and Minitab Using Minitab Software 7
B How do you specify a one sided tolerance for an MSA in Minitab v 16 Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 6
S 'No %Tolerance Is Calculated' Note (Minitab) Using Minitab Software 7
Marco Bernardi Concentricity Tolerance: A Unilateral Boundary Situation (Minitab) Using Minitab Software 22
M Minitab Type 1 Repeatability & GRR% of Tolerance Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 1
B Minitab Comps of Variation Graph has % to Tolerance at 3 million %? Using Minitab Software 2
B Minitab v15 Precision to Tolerance does not compute? Using Minitab Software 1
M % Tolerance Results in Minitab Using Minitab Software 17
V MINITAB and non-normal unilateral tolerance data - Cannot confirm Ppk values Using Minitab Software 15
F Minitab 19 Anova or X bar # of distinct catagories Using Minitab Software 1
P Pooled Standard Error - Minitab Statistical Analysis Tools, Techniques and SPC 0
S Asterisk in DOE minitab software Using Minitab Software 23
B Does anybody know how to get older versions of Minitab to work in Windows 10? Quality Tools, Improvement and Analysis 9
M Minitab Capability of the Population (no sampling) Using Minitab Software 11
Z Minitab - Updating Graph with specific data points Using Minitab Software 2
S Need help with analysing a survey on minitab Using Minitab Software 1
M Minitab assistant: 1-Sample % Defective Test Using Minitab Software 1
0 Interesting Discussion Analysis of half normal distribution in minitab Using Minitab Software 11
G Batch printing reports in Minitab Using Minitab Software 3
B Minitab Type 1 Gage Study on True Position Question Measurement Uncertainty (MU) 1
V Minitab GRR crossed Xbar and r method macro needed Using Minitab Software 9
I Number of decimals in equation calculated by MiniTab Using Minitab Software 0
A Acceptance p-value for linearity and bias analysis in minitab results Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 0
M How to change the display of optimization plot in Minitab 18 Using Minitab Software 2
M Minitab tool to evaluate PM (Preventive Maintenance) process Using Minitab Software 6
E Input to ANOVA 1-WAY - How can I perform this analysis in minitab? Using Minitab Software 2
J Including Repeats in DoE using Minitab Using Minitab Software 5
A Minitab 18: How to automate GRR Summary Table save Reliability Analysis - Predictions, Testing and Standards 1
N What subcommands can be used with "Stop" in Minitab 18? Using Minitab Software 8
S Minitab - Factor Analysis: Label on second series of data for Biplot Using Minitab Software 4
J Which Anova dropdown to use for R&R in Minitab? Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 1
J DoE - Number of runs in Plackett-Burman (Minitab) Using Minitab Software 2
D Asterix when pasting a column of values from Excel into Minitab (V17) Using Minitab Software 5
A Generating samples from a population in Minitab Using Minitab Software 0
Ron Rompen Random data generation in Minitab Statistical Analysis Tools, Techniques and SPC 2
I DOE: High variance and small effects in Minitab Using Minitab Software 1
B Informational Expanded Gage R&R Analysis using Minitab Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 18
R Rank Deficiency Error Minitab Using Minitab Software 7
H Minitab 15 - Factorial Design - 3 factors: 4x3x2 - How to? Using Minitab Software 4
A Capability Analysis for Packaging Seal Strength with spec. >0.1 Kgf using Minitab Using Minitab Software 6
Coury Ferguson MiniTab 17 Question-Standard Deviation Default Capability, Accuracy and Stability - Processes, Machines, etc. 5
N Regression Model (Minitab 18) - Which values my input parameters should have Using Minitab Software 2
L MINITAB 17 - Changing Data Using Minitab Software 3
R Conjoint Analysis - Minitab 18 Statistical Analysis Tools, Techniques and SPC 2
F How to make an ANOVA of a design with repeats (not replicates) in Minitab? Using Minitab Software 18
W Definitive screening design in Minitab 17 Manufacturing and Related Processes 1
S Minitab runs at different speeds on identical PCs Using Minitab Software 5
S Response Surface Method to create design matrix in Minitab Using Minitab Software 5
S Minitab limit definition from R & R Using Minitab Software 4

Similar threads

Top Bottom