# Calculation of Standard deviation, Cp & Cpk in SPC

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

From above screen I have taken below reading 1. Calculation of Mean value

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

Mean Value     = 38.667

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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• good example on calculating Cp, CpK.

• Hi Rajesh,

Good one. What master data settings are maintained to calculate mean, Cp and Cpk?

Thanks & Regards,

Ramagiri

• Most of it is statistics knowledge.

• How do you display Process Capability window for given results?

• Hi Rajesh,

Good Documents.

Regards,

Dipeshkumar Bhavsar

• 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%

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

Actually, which is the target value?