Process capability index - asymmetrical positioning, Operation Management

Assignment Help:

Process Capability Index - Asymmetrical Positioning of the Process

As stated earlier, the Cp index assumes that the process mean is centred within the tolerance band, but, in practice, this is often an unreasonable assumption. For this reason, alternative indices have been devised which take account of asymmetrical positioning of the process mean relative to mid-tolerance. Consider the process output represented in this next figure, for which the LSL is 10, the USL is 20, the process mean (µ) is 18 and the standard deviation (σ) is 1.166. For this process the Cp index value is 1.43 [i.e. (20 - 10)/ (6 × 1.166)], which might suggest that the output has a very low level of non-conformance. However, as can be seen from the figure, a significant proportion of the output actually lies beyond the upper specification limit. The Cpk index takes account of the asymmetry by relating the spread of one side of the output distribution (3σ) to the difference between the process mean (µ) and the nearest specification limit. Two calculations are performed, and the lowest value (worst case) is taken as the index value.

1148_Process Capability Index – Asymmetrical Positioning of the Process.png

In the example in the figure above, the Cpk index is 0.57 [ie (20 - 18)/(3 × 1.166)], indicating that the process, as currently set, is not capable of producing to the design specification. The following figure shows the significance of different Cpk values.

1302_Process Capability Index – Asymmetrical Positioning of the Process 1.png


Related Discussions:- Process capability index - asymmetrical positioning

Explain successful personal selling philosophy, According to the Strategic/...

According to the Strategic/Consultative Selling Model, what are the three prescriptions for developing a successful personal selling philosophy?

Explain what percentage of parts will not meet the weight, Specifications f...

Specifications for a part for a DVD player state that the part should weigh between 24.4 and 25.4 ounces. The process that produces the parts has a mean of 24.9 ounces and a standa

Explain the effective rate of interest for an investment, Find the effectiv...

Find the effective rate of interest for an investment that earns 5 (1/2) % per year, compounded continuously

Describe what the advantages of making vs buying, You are the Vice-Presiden...

You are the Vice-President of Manufacturing for a company which manufactures small personal appliances. Your R & D department has designed a revolutionary, new type of electric t

Explain effective project chartering process, Effective project chartering ...

Effective project chartering process contains multiple project types and projects laid out on a month to month basis.

Explain permissive actions act, Why do unions emphasize the need for cohesi...

Why do unions emphasize the need for cohesiveness? So they can issue calls for "solidarity" to members during periods of threat Because group members tend to behave different

Explain applicable federal regulations relating to kickbacks, Identify and ...

Identify and discuss applicable federal regulations relating to kickbacks

Develop an aggregate plan for helter industires, Helter Industires, a compa...

Helter Industires, a company that produces a line of women's bathing suits, hires temporaries to help produce its summer product demand. For the current four-month rolling schedule

Explain machine on the basis of after-tax present, A low-cost airline opera...

A low-cost airline operating in South Africa is considering adding either Boeing 737-400 or Boeing 737-800 to its fleet. The following information is prepared for the economic eval

Significance of collecting information about competitors, Discuss the impor...

Discuss the importance of collecting information about competitors? Distinguish between ethical and unethical methods of gathering competitive intelligence.

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd