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Yield calculation

Discussion in 'SPC - Statistical Process Control' started by Karthikk, Mar 19, 2024.

  1. Karthikk

    Karthikk New Member

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    I come across a formula in a Dimension sheet for calculating yield but could not comprehend it . Can someone help me to understand the logic behind it ?

    1 material - 16 samples are measured and CP , CPK are calculated as well but below formula used for yield calculation :

    Formula : Normsdist(3*CPK) or Normsdist(3*CPK)+Normsdist(6*CP-3*CPK)-1.
     
    Karthikk, Mar 19, 2024
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  2. Bev D

    Bev D Moderator Staff Member

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    Normsdist is an EXCEL function that returns a value from the Normal distribution table. The calculation is used to return a defect rate for a theoretical Normal distribution based on the ‘coverage’ of the distribution represented by the Cpk value (using the total standard deviation and not the within subgroup variation).
    16 samples is far too lo for this theoretical yield prediction to be accurate. But if that is the requirement then you are stuck…
     
    Bev D, Mar 19, 2024
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    Andy Nichols likes this.