Cp, Cpk for One Sided Specification

[ashram]

Dear all,
I want to calculate cp,cpk for specification given on one sided.
my specification is 20 +0.180
+0.270

so how can I consider its Upper scale and lower scale limits.
Please Help ME.

[alspread]

Is this the same as 20.225 +/-.045?

(20 + .180 = 20.180 20 + .270 = 20.270)

(20.270 - 20.180 = .090 .090/2 = .045)

(20.180 + .045 = 20.225 therefore 20 +.180/+.27- = 20.225 +/-.045)

What value is your process attempting to target?

[bobdoering]

In Reply to Parent Post by ashram

I want to calculate cp,cpk for specification given on one sided.
my specification is 20 +0.180/+0.270

so how can I consider its Upper scale and lower scale limits.
Please Help ME.

USL (Upper Spec Limit) = 20 + .270 = 20.270

LSL (Lower Spec Limit) = 20 + .180 = 20.180

Those two points from your specification are all the Cp and Cpk need for calculation. Beyond that, all that is needed is whether the distribution is normal. If not, then the calculation may not apply anyway.