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Controlling Variability Is More Difficult Than Controlling Mean

A case study of jumping teenagers

Jim Frost
Fri, 12/02/2011 - 15:01
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In a recent blog post, “Assessing Variability for Quality Improvement,” I showed how measuring variability is as important as measuring the mean for a product or service in a quality improvement initiative. The mean, by itself, often tells an incomplete story. Additionally, quality management veterans know that controlling the variability is often more difficult than controlling the mean. If you want to change the mean, it often entails adjusting a manufacturing setting or target. However, reducing variability often requires new technology or procedures.

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For example, in the image below, it’s generally easier to re-center the tightly clustered measurements on a target than it is to reduce the spread of the dots that are centered.

https://lh4.googleusercontent.com/5woV8v3UtOGP8-mK-a9TZ78uyhDI7hWzCvhsIpYLaUanu9Po-l1nT2ed24KLywbxKsLmGlQhl1OtWhXsrdgZFpSURg8mubTOgFqcWajpwqPp-4SYYqQ

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Comments

Submitted by lagomcurt on Tue, 12/06/2011 - 06:06

Begging the question

At risk of being accused of raising irrelevant issues, I have to comment on this sentence:"This begs the question: Can we train the subjects to land a certain way?"  "Begging the question" (Latin petitio principii) is a form of logical fallacty in which an argument is assumed to be true without evidence other than the argument itself.  I think you meant to say, "This raises the question..." (See begthequestion.info)

This was a good, thoughtful article that could be improved through the accurate use of language.

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Submitted by Jim Frost on Tue, 12/06/2011 - 06:23

In reply to Begging the question by lagomcurt

Re: Begging the question

Thanks, I'm glad you enjoyed the article. You are likely correct about the original meaning. However, the Cambridge Dictionary of American Idioms does agree with my current usage of the idiom. 

beg the question

1. to cause a particular question to be asked

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Submitted by lagomcurt on Tue, 12/06/2011 - 12:50

Sorry

Sorry, but I guess I still expect quality professionals to use their language as carefully as they do their statistics.

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