1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.
Dismiss Notice
You must be a registered member in order to post messages and view/download attached files in this forum.
Click here to register.

DOE & GRR

Discussion in 'DOE - Design of Experiments' started by _Zeno_, Oct 15, 2015.

  1. _Zeno_

    _Zeno_ Member

    Joined:
    Sep 3, 2015
    Messages:
    46
    Likes Received:
    20
    Trophy Points:
    7
    How does GRR affect DOE design and interpretation?
     
    _Zeno_, Oct 15, 2015
    #1
  2. Miner

    Miner Moderator Staff Member

    Joined:
    Jul 30, 2015
    Messages:
    657
    Likes Received:
    566
    Trophy Points:
    92
    Location:
    Greater Milwaukee USA
    A GRR should be performed prior to designing an experiment to ensure that you can trust your measurement system. If the measurement system has excessive variation, it could mask the very effects that you want to see in the experiment by inflating the Residual Error portion of the ANOVA table. If you properly calculate the number of replicates in advance, measurement variation could require a larger number of replicates than would otherwise be necessary. At a minimum, you would need to run repeats and average them.

    It is better to have a good measurement device with minimal variation.
     
    Miner, Oct 15, 2015
    #2
  3. Bev D

    Bev D Moderator Staff Member

    Joined:
    Jul 30, 2015
    Messages:
    673
    Likes Received:
    731
    Trophy Points:
    92
    Location:
    Maine
    Interpretation: A large amount of measurement variation will be seen as part variation (aka 'noise') in either graphical or statistical analysis of the DoE results. This could result in missing true differences in either main effects or interactions.

    Design: If you have minimal measurement variation then you can get by with a smaller sample size for each trial. If you have substantial measurement variation taht you cannot easily reduce, you will need to increase your sample size for each trial.

    I recommend checking out the following in the Resources section of this forum. (Resources tab is on the upper left hand area next to the forums tab)

    MSA for Functional Tests: page 6 and 7 explain an MSA with a large amount of measurement variation and a compensation scheme.

    Profound Statistical Concepts Part 2 Example 1: This example shows a classical DoE (3 factors, 2 levels) with horrible measurement error.


    You might also find these useful:
    The Statistical Foundation Cracks in the Popular Gauge R&R Method
    MSA Verification and Validation
     
    Bev D, Oct 15, 2015
    #3