The process capability measures Cp and Cpk differ because
A) only one ensures the process mean is centered within the limits
B) Cp values above 1 indicate a capable process, Cpk values above 2 indicate a capable process
C) both are identical
D) Cp values for a given process will always be greater than or equal to Cpk values
E) both A and D

Question

Quizplus · Accepted Answer

Cp only measures the process capability with regard to the spread of the data and does not take into account the location of the process mean relative to the specification limits. On the other hand, Cpk considers both the spread of the data and the position of the process mean within the specification limits. Therefore, Cp values can be greater than or equal to Cpk values depending on the location of the process mean. Thus, statement A and D are correct, which makes option E the best choice. Option B is incorrect because there are no fixed values that indicate a capable process; rather, it depends on the specific process and its requirements. Option C is also incorrect because the two measures are not identical in their calculation or interpretation.

The Process Capability Measures Cp and Cpk Differ Because