Publications by Matt Bogard
Why does IFELSE logic work differently on what appear to be the same values?
Embarrassingly I’m stumped on this…I have a program in R for looking at grade distributions in my class. I found something weird recently with my ‘ifelse’ processing. I noticed that my program seemed to be over counting Cs and under counting Bs. I’m not sure what’s going on. It happened in the case where I was adding...
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A Toy Instrumental Variable Application
I have previously discussed instrumental variables (hereand here) from a somewhat technical standpoint, but now I’d like to present a very basic example with a toy data set that demonstrates how IV estimation works in practice. The data set below is fabricated for demonstration purposes. The idea is to develop intuition about the mechanics of...
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Using the R MatchIt package for propensity score analysis
Descriptive analysis between treatment and control groups can reveal interesting patterns or relationships, but we cannot always take descriptive statistics at face value. Regression and matching methods allow us to make controlled comparisons to reduce selection bias in observational studies. For a couple good references that I am ba...
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SAS vs R? The right answer to the wrong question?
For a long time I tracked a discussion on LinkedIn that consisted of various opinions about using SAS vs R. Some people can take this very personal. Recently there was an interesting post at the DataCamp blog addressing this topic. They also provided an interesting infographic making some comparisons between SAS and R as well as SPS...
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Divide by 4 Rule for Marginal Effects
Previously I wrote about the practical differences between marginal effects and odds ratios with regard to logistic regression. Recently, I ran across a tweet from Michael Grogan linking to one of his posts using logistic regression to model dividend probabilities. This really got me interested:“Moreover, to obtain a measure in prob...
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