Content by Donald J. Wheeler
The Imaginary Theorem of Large SamplesHow many data samples do you need?
Mon, 04/05/2010 - 10:10
Courses in statistics generally emphasize the problem of inference. In my December column, “The Four Questions of Data Analysis,” I defined this problem in the following manner:
Given a single unknown universe, and a sample drawn from that… Scaling Factors for Process Behavior ChartsA quick reference guide
Mon, 03/01/2010 - 05:00
In the 1940s the War Production Board trained approximately 50,000 individuals in how to use process behavior charts (also known as control charts). At that time the computations were done by hand, and the emphasis was on making things as easy as… Individual Charts Done Right and WrongHow does your software rate?
Mon, 02/01/2010 - 05:00
In my column of Jan. 7, “The Right and Wrong Ways of Computing Limits,” I looked at the problems in computing limits for average charts. This column will consider the right and wrong ways of computing limits for charts for individual values. As… The Right and Wrong Ways of Computing Limits How does your software measure up?
Thu, 01/07/2010 - 05:00
Today virtually everyone uses software to create process behavior charts, yet the available software is notoriously unreliable in terms of the way the limits are computed. This column will explain and illustrate the difference between the correct… The Four Questions of Data AnalysisHomogeneity is the primary question of analysis.
Tue, 12/01/2009 - 05:00
The four questions of data analysis are the questions of description, probability, inference, and homogeneity. Any data analyst needs to know how to organize and use these four questions to be able to obtain meaningful and correct results.
The… Two Definitions of TroubleLead us not into the Cycle of Despair
Mon, 11/02/2009 - 04:00
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n the past there was only one criterion required to be a good supplier: you had to ship very few nonconforming items. If your proportion of nonconforming items took a turn for the worse then you would be “in trouble,” and you would stay in… Avoiding Statistical JabberwockyThe last column in the debate between Donald Wheeler and Forrest Breyfogle
Wed, 10/07/2009 - 05:00
This is the final column in the debate between Donald Wheeler and Forrest Breyfogle on whether or not to transform data prior to analysis. Because the debate started with Wheeler's article "Do You Have Leptokurtophobia?" we are letting him have the… Transforming the Data Can Be Fatal to Your AnalysisIf you think you really know your data, look again.
Thu, 09/03/2009 - 05:00
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 III to write the response. However, rather than… Do You Have Leptokurtophobia?The abnormal need for normal distributions
Wed, 08/05/2009 - 05:00
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 you have exhibited either of these symptoms then… Good Limits From Bad DataWhat if the range chart is “out of control?”
Mon, 07/06/2009 - 03:00
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 subject of this column.
To illustrate the issues we…
