Blog Archives

If SPSS can factor analyze MaxDiff scores, why can’t R?

January 17, 2013
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If SPSS can factor analyze MaxDiff scores, why can’t R?

Answer:  The variance-covariance matrix containing all the MaxDiff scores is not invertible.  R tells you that, either with an error message or a warning.  SPSS, at least earlier versions still in use, runs the factor analysis witho...

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Warning: Sawtooth’s MaxDiff Is Nothing More Than a Technique for Rank Ordering Features!

January 14, 2013
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Sawtooth Software has created a good deal of confusion with its latest sales video published on YouTube.  I was contacted last week by one of my clients who had seen the video and wanted to know why I was not using such a powerful technique for me...

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Item Response Modeling of Customer Satisfaction: The Graded Response Model

January 8, 2013
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Item Response Modeling of Customer Satisfaction:  The Graded Response Model

After several previous posts introducing item response theory (IRT), we are finally ready for the analysis of a customer satisfaction data set using a rating scale.  IRT can be multidimensional, and R is fortunate to have its own package, mirt, with excellent documentation (R.Philip Chalmers).  But, the presence of a strong first principal...

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PLS Path Modeling with R: A Comprehensive Tutorial by Gaston Sanchez

January 6, 2013
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PLS Path Modeling with R: A Comprehensive Tutorial by Gaston Sanchez

Gaston Sanchez has just published an online pdf of his new book PLS Path Modeling with R.I have been using Gaston's plspm r package for a couple of years to analyze marketing data.  I started when I needed to test a path model in wh...

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Searching for Structure underlying Customer Satisfaction Ratings: Item Response Theory through the Back Door

December 30, 2012
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Searching for Structure underlying Customer Satisfaction Ratings: Item Response Theory through the Back Door

Variations on a Theme of Negative Skew and Positive ManifoldNo one familiar with research on customer satisfaction expects to find uncorrelated ratings or symmetric distributions centered toward the middle of the rating scale.  There are forces at work that structure the means and correlations among the items from a customer satisfaction questionnaire.  On the one hand, unsatisfied customers churn,...

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Making Friends with Multicollinearity

December 18, 2012
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Not every system of independent variables can be decomposed into separate components, each with its own unique contribution.  Sometimes our individual variables behave “as a unit” and thus become so entangled that we cannot say where the effect of one variable begins and the effect of another variable ends.  In such cases, it might be best to ignore the ...

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Clarifying a Previous Item Response Theory Link

December 11, 2012
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I wanted to thank those of you who have emailed and commented on my last post and its Link to Item Response Theory Presentations Using R.  In the Psychometrics Centre website, it is not until Topic 7 called Unidimensional IRT models for binar...

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Link to Item Response Theory Presentations Using R

December 6, 2012
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After my post on item response theory,  a number of you have asked for links to applications that provide R code.  As I noted in that post, a good deal of work is being done in an area of research called patient-related outcome measurement (P...

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How Microsoft Can Use Windows 8 to Dominate the Tech Industry

November 9, 2012
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How Microsoft Can Use Windows 8 to Dominate the Tech Industry

Windows 95 transformed the PC software market and established Microsoft as the dominant player.  Can Microsoft do it again?  Can it use the release of Windows 8 to elevate its entire brand image?  More importantly to some of us, can Microsoft use statistical modeling to help it achieve its goal?Of course, the answer depends on what you mean by...

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A Brief Tip on Generating Fractional Factorial Designs in R

October 1, 2012
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A number of marketing researchers use the orthoplan procedure in SPSS to generate fractional factorial designs.  It is not surprising, then, that I received a number of questions concerning the recent article in the Journal of Statistical Software by Hideo Aizaki on “Basic Functions for Supporting an Implementation of Choice Experiments in R.”  To summarize their issues,...

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