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Parts Per Million implementation/ calculation

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A supplier is compressions molding a silicon part. For this production process I am thinking of creating/ calculate PPM (Parts Per Million). Since supplier manufacturer 10,000 to 20,000 parts per lot, its not feasible to visually check every part in the lot for defective units to calculate the PPM


Can you give me guidelines on selecting samples from the lot to calculate the PPM.

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  • 5 months later...

For acceptance sampling plans you should start with defining the distribution. E.g. if we assume a Binomial distr. we need to define the alpha risk, the success probability for the consumer risk, the the beta risk, and the success prob. for the beta risk. Once you have these values it is strait forward to calc the sample size. If you instead use a hypergeometric distr. you should also define the batch size.


Note that you will need many samples, if you like to verify that your failure rate is only a few ppm. 

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