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Brad Gover - 2010
Hi all,
I have a question on how to apply and interpret the use of Study variation and discrimination ratio. Some people at my company set up an MSA with made up sample ranges. For example, the MSA of an analytical balance was set up to have weight samples spanning the range of the gauge's ability to measure (0.001grams to 200. grams). The measurement results from two operators three trials were given to me for analysis. I calculated the values and got a study variation of 0.00% and a discrimination ratio of 148,000. I have a part to part standard deviation of 12.48 with a total GR&R standard dev of 0.0001. All that makes sense to me. The problem I have is the samples do not have anything to do with any process here. Others claim that we're not looking at the process, only the gauge. My problem is by not having samples that span the variation of some process (not just measuring a range of weights) makes the study variation and DR meaningless. They want to say the MSA is acceptable due to the outcomes of the study. Should the samples always be pulled from the process or can you arbitrarily make up samples to analyze the gage only? How should the conclusion with the report on Study variation and DR address this?
Thanks for the input.
I have a question on how to apply and interpret the use of Study variation and discrimination ratio. Some people at my company set up an MSA with made up sample ranges. For example, the MSA of an analytical balance was set up to have weight samples spanning the range of the gauge's ability to measure (0.001grams to 200. grams). The measurement results from two operators three trials were given to me for analysis. I calculated the values and got a study variation of 0.00% and a discrimination ratio of 148,000. I have a part to part standard deviation of 12.48 with a total GR&R standard dev of 0.0001. All that makes sense to me. The problem I have is the samples do not have anything to do with any process here. Others claim that we're not looking at the process, only the gauge. My problem is by not having samples that span the variation of some process (not just measuring a range of weights) makes the study variation and DR meaningless. They want to say the MSA is acceptable due to the outcomes of the study. Should the samples always be pulled from the process or can you arbitrarily make up samples to analyze the gage only? How should the conclusion with the report on Study variation and DR address this?
Thanks for the input.
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