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Foe below result achieved see calculation of how Mean Value, Standard deviation, Cp & Cpk is calculated in standard SAP

SPC calculation 1.jpg

See below result of Mean Value, Standard deviation, Cp & Cpk is calculated in standard SAP

SPC calculation 2.jpg

From above screen I have taken below reading

SPC calculation 3.jpg

1. Calculation of Mean value

So Mean Value,    = (Sum of Recorded Result) / No. of Record

                         

SPC calculation 4.jpg

          Mean Value     = 38.667                       

SPC calculation 5.jpg                 

SPC calculation 6.jpg                     

The mean (38.667) is closer to one of them than to the other, leading to a Cpk factor (0.17) that is lower than the Cp value (0.22). This implies that the LSL is more difficult to achieve than the USL. Non-conformities exist at both ends of the histogram.

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6 Comments

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  1. venkat t

    Hi,

    How do to select USL and LSL limits?

    For example,

    I have measured results of 30 samples Re is 3.43, 3.27 ,3.19, 3.17,3.17, 3.19, 3.19, 3.24, 3.1, 3.12 ,3.25, 3.2, 3.35, 3.2, 3.2, 3.22, 3.23, 3.18, 3.19, 3.31, 3.18, 3.08, 3.18, 3.17, 3.23, 3.19, 3.25, 3.26, 3.23, 3.18

    mean = 3.2117, STD = 0.07

    Company datasheet provided for Re is 3.08 and production tolerances +/- is 7.50%

    ——–
    to find Cpk how do I calculate USL and LSL values?

    Actually, which is the target value?

    (0) 

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