Publications by Joel Cadwell
Clarifying a Previous Item Response Theory Link
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 binary data that we get to the R code for the ltm package. You need to download the data file ...
2181 sym
Making Friends with Multicollinearity
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...
4643 sym
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 questio...
12143 sym 4 img 2 tbl
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 which one of the latent variables was a formative measure with far too many sparse indicators. S...
2318 sym 2 img
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 comp...
17666 sym 10 img 3 tbl
Warning: Sawtooth’s MaxDiff Is Nothing More Than a Technique for Rank Ordering Features!
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 measuring attribute importance. “It gives you a ratio scale,” he kept repeating. And that is...
9070 sym
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 without comment.I made two points in my last post. First, if you want to rank order your attributes, yo...
10345 sym 2 img
Reducing Respondent Burden: Item Sampling
You received confirmation this morning. Someone made a mistake programming that battery of satisfaction ratings on your online survey. Instead of each respondent rating all 12 items using a random rotation, only six randomly selected items were shown to any one respondent. As a result, although you have ratings for all 12 items...
9280 sym 2 img
Incorporating Preference Construction into the Choice Modeling Process
Statistical modeling often begins with the response generation process because data analysis is a combination of mathematics and substantive theory. It is a theory of how things work that determines how we ought to collect and analyze our data.A good example of this type of statistical modeling was the accurate predictions ma...
13496 sym
When Discrete Choice Becomes a Rating Scale: Constant Sum Allocation
Why limit our discrete choice task to next purchase when we can ask about next ten purchases? It does not seem appropriate to restrict choice modeling to one selection only when repeat purchases from the same choice set are made by the same individual buying different products at different times. Similarly, a purchasing ag...
7227 sym