Minitab 14 vs. Excel .xls spreadsheet differences? MSA Manual 3rd Edition

[justncredible]

Attached is a excel GR&R and a mintab 14 GR&R. The data is the same, the numbers and NDC are diffrent making the excel sheet FAIL. I am a professed "noob" with MSA, so can maybe the more learned explain why they are not jiving?

Is the math right on the excel sheet, since I pray it is right in MT. I want to include the excel sheet to show the big PASS/FAIL since it most likley will not be viewed expert GR&R people.

Has anyone found a sheet that matches the math in minitab? Or has anyone ever checked the math on the sheets and in minitab?

 

[Miner]

The main reason for the difference is that the Excel spreadsheet is set up as a "Crossed" study, which is how 95% of MSA studies are designed. Crossed means that all operators test all parts repeatedly.

The Minitab analysis that you selected is a "Nested" design. This typically means that each operator tests a different set of parts. Minitab also has a "Crossed" option that you should use in most situations.

If you want Minitab to achieve identical results to your spreadsheet, use the "Crossed" option and the Xbar/Range method.

Be careful with the results of cells M44 and M45 in your spreadsheet. You will typically use the results of cell K42 (%GRR) OR M42 (P/T Ratio) to make a decision on the suitability of the gage, NOT the minimum of the two. The logic in cells M44 and M45 is flawed. You could add a toggle option to state whether to use %GRR OR P/T Ratio to make the decision and change the logic in cells M44/M45 accordingly. In a less common situation, you may need to use both, but the logic is still flawed for this situation.

 

[Yew Jin]

Additional info when we conduct GR&R on excel spreadsheet and minitab.....

By default, minitab chooses 6 instead of 5.15 as a multiplier factor to represent 99.73% coverage level. Most of the excel spreadsheet for GR&R is using 5.15 which represent convention 99% spread.

 

[Miner]

Additional info when we conduct GR&R on excel spreadsheet and minitab.....

By default, minitab chooses 6 instead of 5.15 as a multiplier factor to represent 99.73% coverage level. Most of the excel spreadsheet for GR&R is using 5.15 which represent convention 99% spread.

Thanks Yew. I overlooked that possibility.

I just checked his spreadsheet and it does use the 3rd edition constants (i.e., 6 multiplier), so this is not the cause.

 

[Jim Shelor]

Attached is a excel GR&R and a mintab 14 GR&R. The data is the same, the numbers and NDC are diffrent making the excel sheet FAIL. I am a professed "noob" with MSA, so can maybe the more learned explain why they are not jiving?

Is the math right on the excel sheet, since I pray it is right in MT. I want to include the excel sheet to show the big PASS/FAIL since it most likley will not be viewed expert GR&R people.

Has anyone found a sheet that matches the math in minitab? Or has anyone ever checked the math on the sheets and in minitab?

You are using variations in your spreadsheet for calculating NDC. NDC is calculated using sigma, not variation.

Jim Shelor
PMP, SSBB