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Nonparametric Statistics

Blog posts and articles about using statistical software to apply nonparametric statistics in quality improvement.

Do you suffer from PAAA (Post-Analysis Assumption Angst)? You’re not alone. Checking the required assumptions for a statistical  analysis is critical. But if you don’t have a Ph.D. in statistics, it can feel more complicated and confusing than the primary analysis itself. How does the cuckoo egg data, a common sample data set often used to teach analysis of variance, satisfy the following formal... Continue Reading
There is more than just the p value in a probability plot—the overall graphical pattern also provides a great deal of useful information. Probability plots are a powerful tool to better understand your data. In this post, I intend to present the main principles of probability plots and focus on their visual interpretation using some real data. In probability plots, the data density distribution... Continue Reading
My main objective is to encourage greater use of statistical techniques in the service sector and present new ways to implement them. In a previous blog, I presented an approach you can use  to identify process steps that may be improved in the service sector (quartile analysis). In this post I'll show how nonparametric distribution analysis may be implemented in the service sector to analyze... Continue Reading
In my home, we’re huge fans of Mythbusters, the show on Discovery Channel. This fun show mixes science and experiments to prove or disprove various myths, urban legends, and popular beliefs. It’s a great show because it brings the scientific method to life. I’ve written about Mythbusters before to show how, without proper statistical analysis, it’s difficult to know when a result is statistically... Continue Reading
  “Shall I compare thee to a standard normal distribution?   Thou art more symmetric and more bell-shaped…”  — Melvin Shakespeare (William’s lesser-known statistician brother) The Greek philosopher Aristotle believed that symmetry was one of the primary elements of the universal ideal of beauty. Over 2000 years later, emerging research seems to bear him out.  Studies suggest we tend to be more... Continue Reading
Watching the news in the U.K. is like listening to the same old annoying record over and over again: "Uncertainties about the European economy...disappointing employment figures...stubbornly  high inflation...increasing pressures on  the average U.K.  household  to make ends meet…" How about some good news, please? Actually, there is some good news…that is, if you are a top executive for one of the... Continue Reading
I am an outlier. Of the people who work in my department, I go to the fewest meetings, I talk with others the least, and I make the least use of our exercise facilities. But this is not because I am negligent, anti-social, or lazy. It is because I am separated from the rest of my department by about 10,000 miles.You see, my family and I have had the opportunity recently to move to beautiful... Continue Reading
We humans do have a tendency to succumb to gold rush fever. And this can happen even in the left-brained, rational field of statistics. After we collect our data, it’s difficult to resist the urge to desperately dash for p-values, as if they were 70% off at Macy’s the day after Thanksgiving.But no matter how well-versed you are in statistics, it’s good practice to get into the habit of intuitively... Continue Reading