Selected Publications

As the use of diagnostic assessment systems transitions from research applications to large-scale assessments for accountability purposes, reliability methods that provide evidence at each level of reporting must are needed. The purpose of this paper is to summarize one simulation-based method for estimating and reporting reliability for an operational, large-scale, diagnostic assessment system. This assessment system reports the results and associated reliability evidence at the individual skill level for each academic content standard and broader content strands. The system also summarizes results for the overall subject using achievement levels, which are often included in state accountability metrics. Results are summarized as measures of association between true and estimated mastery status for each level of reporting.

This graphic shows the probability of providing a correct response to an item in a multidimensional item response theory (MIRT) model. In the 1PL, 2PL, and 3PL MIRT models, the choice of compensatory parameterizations can greatly affect the probability of a correct response.

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I have once again been inspired by a tweet! This one came from @WeAreRLadies, which was being moderated by Alison Hill at the time. Y'all there is a ggclock @rstudio #ggplot2 #rstats — We are R-Ladies (@WeAreRLadies) November 9, 2018 Alison was at RStudio headquarters in Boston, when she noticed a ggplot2 themed clock! To which I had a totally normal reaction. I decided that I must have one.


Earlier this week Mike Bostock tweeted a interesting looking contour plot with a link to edit the formula and manipulate the graphic using D3.js. A live 2D function plot. Edit the function and reply with interesting images! — Mike Bostock (@mbostock) September 3, 2018 I decided I would attempt to recreate the image using ggplot2, and animate it using the new gganimate package. Creating the data I started by creating a data frame with all the combinations of x and y on a grid between -10 and 10, in intervals of 0.


Recently I’ve been looking for an excuse to try out Thomas Lin Pedersen’s new grammar of animation, which is an extension of ggplot2 and a retooling of the existing gganmiate package. You can find the new package here. Luckily for me, Rafael Irizarry provided the perfect inspiration: Happy #MayFourth #rstats par(bg=1,fg="white") x<-0.5->y z<-"|-o-|" s<-cbind(runif(50),runif(50)) m<-c(-1,1)/20 while(TRUE){ rafalib::nullplot(xaxt="n",yaxt="n",bty="n") points(s,pch=".") text(x,y,z, cex=4) x<-pmin(pmax(x+sample(m,1),0),1) y<-pmin(pmax(y+sample(m,1),0),1) } — Rafael Irizarry (@rafalab) May 4, 2018 So in honor of Star Wars day, I decided to create Rafael’s TIE fighter GIF using the new gganimate.



Bayesian Regression Modeling with rstanarm

DataCamp course introducing Bayesian methods for linear regression using the rstanarm package.

Evaluating Model Estimation Processes for Diagnostic Classification Models

PhD dissertation submitted to the University of Kansas


Template for writing theses at the University of Kansas using rmarkdown and bookdown.

Soccer predictions using Bayesian mixed effects models

Models developed for the prediction of individual games, European domestic leagues, and the UEFA Champions League.


More Publications

  • Using simulation to evaluate retest reliability of diagnostic assessment results


  • Measuring the reliability of diagnostic mastery classifications at multiple levels of reporting


  • A hierarchical model for identifying group-level aberrant growth to detect cheating


  • Construct Irrelevant Variance

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  • Visualizing different levels of compensation in multidimensional item response theory models

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