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 making and marketing the new product, Mary Williams, owner of Willi...

Mary Williams, owner of Williams Products, is evaluating whether to introduce a new product line. After thinking through the production process and the costs of raw materials and n

Describe departments being located close together, A (n) ____ gives the rel...

A (n) ____ gives the relative importance of each pair of operations or departments being located close together.

How investment to double, To the closest year, how long will it take a $200...

To the closest year, how long will it take a $200 investment to double if it earns 7 percent interest? How long will it take if it earns 18 percent?

Why a project manager desires a work breakdown structure, A project manager...

A project manager desires a work breakdown structure that goes through 6 levels of detail. Level 3 through level 6 would most likely be prepared by: Answer Project sponsor

Explain what percentage of time are the clerks idle, The parts department o...

The parts department of a large automobile dealership has a counter used exclusively for mechanics' requests for parts. The time between requests can be modelled by a negative expo

Explain to beat the competition to a sale, During the holidays, companies o...

During the holidays, companies often provide gifts to customers. The more a client spends, the larger the gift, usually. To segment customers in this way, for what purpose is this

Explain accounting, Explain accounting. Accounting: It is an art of c...

Explain accounting. Accounting: It is an art of classifying and recording data. Now there data refers to transactions having monetary or financial values. As per to this, acc

Case study, Bloomsday Outfitters produces T-shirts for road races. They nee...

Bloomsday Outfitters produces T-shirts for road races. They need to acquire some new stamping machines to produce 30,000 good T-shirts per month. Their plant operates 200 hours per

Explain what is the null hypothesis, A client gives you a data set of 30 ob...

A client gives you a data set of 30 observed values that represent the number of gallons of gas that 30 individual Nissan Sentra owners purchased at the gas pump last month. Your c

Explain what output rate will be achieved, An assembly line with 30 activit...

An assembly line with 30 activities is to be balanced. The total amount of time to complete all 30 activities is 42 minutes. The longest activity takes 2.4 minutes and the shortest

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