Donald J. Wheeler
Following my article on Leptokurtophobics (Do You Have Leptokurtophobia?) it was almost inevitable that we should hear from one. We were fortunate to have someone as articulate as Forrest Breyfogle...
Donald J. Wheeler
The symptoms of leptokurtophobia are (1) routinely asking if your data are normally distributed and (2) transforming your data to make them appear to be less leptokurtic and more “mound shaped.” If...
Donald J. Wheeler
Some authors recommend that you have to wait until you have the range chart “in control” before you can compute the limits for the average chart or the X chart. Why this is not true will be the...
Donald J. Wheeler
Last month we showed the X chart in figure 1. The four lowest values and the three highest values were seen to be “outliers” when we looked at the histogram. When we fitted a bell-shaped curve to...
Donald J. Wheeler
Many have been taught that they must remove outliers prior to analysis. This is because much of modern statistics is concerned with creating a mathematical model for the data. Because all these...
Donald J. Wheeler
As Davis Balestracci frequently emphasized in his column, “RealWorldSPC,” published in Quality Digest for four years, it is fundamental to understand the context of the data before you begin to do...
Donald J. Wheeler
The number of major hurricanes in the Atlantic since 1940 (as we considered in my February column, “First, Look at the Data”) are shown as a histogram in figure 1, below. Some analysts would begin...
Donald J. Wheeler
I recently received a data set consisting of the number of major hurricanes in the North Atlantic from 1940 to 2007. (Major hurricanes are those that reach Category 3 status or higher at some point...
