# Cp Capability Comparison - Page 19 and 20 of the 3rd edition of the MSA manual

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#### dbzman

On page 19 and 20 of the 3rd edition of the MSA manual there is a calculation to determine the following:

1. Observed Cp
2. Actual Cp
3. MSA Cp

When I use the formulas to calculate the examples on page 19 and 20 I do not get the same results. Could someone help me with this?

When I do a substitution into the formulas I can’t get the same numbers.

Thanks!

#### Miner

##### Forum Moderator
dbzman said:
On page 19 and 20 of the 3rd edition of the MSA manual there is a calculation to determine the following:

1. Observed Cp
2. Actual Cp
3. MSA Cp

When I use the formulas to calculate the examples on page 19 and 20 I do not get the same results. Could someone help me with this?

When I do a substitution into the formulas I can’t get the same numbers.

Thanks!

I verified that the calculations are correct on these pages. The two most likely errors are:
• The negative exponents mean: 1/(Cp obs)^2=1/(Cp actual)^2 + 1/(Cp msa)^2
• You need to convert % GRR to an equivalent Cp (e.g., Cp msa = 1/% GRR in decimal form)

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