The ratio of the difference of specification limits and the process spread is known as _______.

Question

Question

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JKSSB JE Mechanical 02 Nov 2021 Shift 1 Official Paper

Answer 1

Explanation:

This question refers to the six sigma quality control in process management.
Finding out the best process as per statistical analysis is essential to minimize the cost of operation as well as to achieve the required quality control.

Process capability:

Process capability is the spread of the process.
If the standard deviation of the process is σ, then process capability is 6σ. It indicates that the process can produce goods within ± 3σ.
If the 6σ of the process lies between USL (upper specification limit) and LSL (lower specification limit), then the process is capable as 99.73% of the goods produced will be within limits.

Potential capability index:

It is the ratio of the difference between specification limits and the process spread.

\(C_p = \frac{USL-LSL}{6\sigma}\)

By convention, when a process has a C_p value less than 1.0, it is considered potentially incapable of meeting specification requirements.
Conversely, when a process C_p is greater than or equal to 1.0, the process has the potential of being capable.
Ideally, the C_p should be as high as possible. The higher the Cp, the lower the variability with respect to the specification limits.
In a process qualified as a Six Sigma process (i.e., one that allows plus or minus six standard deviations within limits of the specifications), the C_p is greater than or equal to 2.0.