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Calculating K1, K2, and K3 for 30 part sample

Discussion in 'Gage R&R and MSA - Measurement Systems Analysis' started by S1D3K1CK, Jan 22, 2021.

  1. S1D3K1CK

    S1D3K1CK Member

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    Hello, our customer requires us to do MSA's for PPAP and E-buy product at the rate of 10% of the E.A.U. or 30 parts, whichever is least. We have a format that was created prior to my start in Quality, that goes to 10 parts, and now I am the lead in Quality due to personnel retiring. I, never having any Quality background prior to my employment here, am not familiar with calculating any of the formulas required for a complete overhaul of a Gage R&R form. I have done some reading in the AIAG manuals and have created a new format but ran into an issue. The format I created is set up for a 30 part or fewer sample data collection but am stumped at completing it with gathering the K3 values up to 30 parts. Is this achievable or am I wasting time here?
     
  2. Miner

    Miner Moderator Staff Member

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    This has been extensively discussed without resolution in the Elsmar Cove forums. The easiest way around this is to use an ANOVA approach instead of the Xbar/Range approach, or to calculate the standard deviation directly rather than using k#*Range.
     
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  3. S1D3K1CK

    S1D3K1CK Member

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    I did some research over the weekend and found helpful software for this. QI Macros has a lot of detail covering almost everything you can think of, with training on some subjects. The software uses ANOVA for their GAGE R&R. I am not familiar with ANOVA but hopefully, this software can guide me and anyone else looking for help.
     
  4. Bev D

    Bev D Moderator Staff Member

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    My response from Elsmar to the same question:

    With a large number of repeated measurements you shouldn't use the range. you need to use the standard deviation.
    1) the range tables do not go beyond n=25 (commonly available tables do not go beyond n=10.) because the formula for d2 is horrendous.
    2) the standard deviation is MUCH more precise at large sample sizes (n>3-5) because it uses all of the data and the range only uses the min and max number.

    Of course to do this without statistical software you need to understand the formulas - you can't treat Gauge R&R as a black box. Actually you shouldn't treat any statistical approach like a black box.
     
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