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Homoscedasticity

For the last couple of columns, we have been analyzing a simple experiment where we look for the best choice for a new gear material. We have used analysis of variance (ANOVA) to detect a difference in the mean wear for the four different materials. In the last column, we performed a post-hoc test to determine which means were actually different from one another. However, to find the best solution, we need to know true costs, and to get that I need to know the variability associated with the different materials. At the end of the article, I’ll give you a chance to show off —the first one to e-mail me the correct cost analysis will get bragging rights and their name (or reasonably tasteful nom de plume if you prefer) in print.

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Was it Colder in Grandpa's Day?

Digging out from a data blizzard

As I’m writing this, our first big snowfall of the year is piling up outside and it is –10°C (15°F). This brings to mind the many times my grandfather told me of how he walked to school in winter uphill (both ways) with no shoes. So I wondered, will I be able to spin the same yarn for my girls and tell them about how much colder it was when I was young? And could granddad have been exaggerating about more than the fish he caught? So (of course) I did what any data-geek would do and downloaded the data. Let’s take a look and see how this time series pertains to Black Belts.

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Sample Size

Greek alphabet soup

Harvest time—vegetables fresh from the local farmer’s market going right into a homemade soup, eaten with fresh bread. Yum! This month, I’d like to talk about a recipe for a Greek alphabet soup, which you had better know about if you plan on doing an experiment. This may be the first recipe that might save your bacon, rather than use it up.

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ANOVA by any other name

By the time you are reading this, you will have made your New Year’s resolutions, and I will have already broken mine. But I have an idea for a resolution that you might be interested in keeping, and one that could make your New Year happy and profitable. It is something that most Black Belts I talk to have never heard of. Before we get there, we need to talk about another powerful tool, with which you may be familiar.

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Measurement System Analysis

Don't judge a gauge by its sticker

I seem to be thinking about the measurement phase a lot recently. I suppose it’s because I’ve seen some teams working hard on problems that turned out to be nothing more than problems with measurement. Let me give you an example.

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Random Heresy

Every once in a while, people ask about acceptance sampling plans and I get all riled up. We all know (especially in this political season) that humans are addicted to their indignation high, so here’s your fix for today.

Back when defective products and services were considered inevitable, the military c

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News Flash

Six Sigma's lead instructor Steven Ouellette wrote an article with Dr. Jeffrey Luftig on "The Decline of Ethical Behavior in Business."

 


 

Six Sigma Online's lead instructor Steven Ouellette was profiled in the June 2008 issue of Quality Digest magazine. If you want to learn more about Steve's peculiar view of the world, as well as what he studied for a year in Europe, read the profile online.

 

 

 

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