It is common for researchers to be concerned about unobserved effects being correlated with observed explanatory variables.For instance, if we were curious about the effect of meditation on emotional stability we may be concerned that there might be so... [Read more...]

# For the purposes of simulating computerized adaptive tests# the R package catR is unparallelled. # catR is an excellent tool for students who are curious about# how a computerized adaptive test might work. It is also useful# for testing companie... [Read more...]

# This post does some basic correlation analysis between responses# to the survey I recently released through R Shiny at:http://www.econometricsbysimulation.com/2013/11/Shiny-Survey-Tool.html # I have saved the data from the survey after completin... [Read more...]

I have written a very basic survey tool built entirely in the Shiny package of R.  I hope the tool is useful.  Modifying the survey for your own purposes is trivially easy (I hope).I have not commented my code so it is pretty messy right now.... [Read more...]

ShinyApps.io is a new server which is currently in alpha testing to host Shiny applications.  It is being designed by the RStudio team and provides some distinct features different from that of the ShinyApps.io is intended for larger applications ... [Read more...]

This post demonstrates the dynamics involved in a susceptible, infected, and recovering (SIR) model previous post for the model.  The shiny ui and server code can be found on GitHub.of dynamic programming. As a dynamic infection model, I find it p... [Read more...]

Ordinary least squares continues to be the staple estimator for causal inference for good reason.  In order to help new and veteran OLS users get a better sense of how it is working I have created a shiny app that allows for instant interactivity ... [Read more...]

# The Poisson distribution has the interesting property that it# models outcomes from events that are independent and equally# likely to occur. The distribution takes only one parameter mu# which is equal to both the mean (expected number of events) #... [Read more...]

# The theoretical basis of classical consumer theory lies# in utility maximization. The idea is that consumers# make consumption decisions based on choosing a bundle # of goods that will maximize individual utility.# Despite this hypothesis being large... [Read more...]

# Han (2012) in the paper "An Efficiency Balanced Information Criterion # for Item Selection in Computerized Adaptive Testing" proposes a method# of evaluating potential items based on expected item potential information # as a function of maximum pote... [Read more...]

Dear Readers,This blog has been going for a year and a half now and I have posted nearly 300 posts to date.  I plan to continue to post though I am going to probably continue to shift my focus from daily blogging to that of getting a dissertation ... [Read more...]

# Reckase (2003) proposes a method for designing an item pool for a computer# adaptive test that has been known as the bin and union method. This method# involves drawing a subject from a distribution of abilities. Then selecting# the item that maximi... [Read more...]

# Maximum likelihood Estimation (MLE) is a powerful tool in econometrics which allows for the consistent and asymptotically efficient estimation of parameters given a correct identification (in terms of distribution) of the random variable. # It i... [Read more...]

Thinknum.com is a new free data service similar to Quandl.com in that they organize and list publicly available data sets.  Currently they are using data from 2,000 data sources which sounds good compared with Quandl's 400+ source.  Overall, ... [Read more...]

One of the most frequently used string recognition algorithms out there is regex and R implements regex.  However, users can often be frustrated with how despite taking examples verbatim from many sources such as stackoverflow they do not seem to ... [Read more...]

# I am working on creating some functions that will be capable of creating shapes and plots that look hand drawn. # I have made some progress in this goal. # In that process I have also discovered that I can make some doodles that look hand d... [Read more...]

This post is written as a result of finding the following exchange on one of the R mailing lists:Is-there-a-way-to-export-regression-output-to-an-excel-spreadsheetQuestion: Is there a way to export regression output to an excel spreadsheet?Translation:... [Read more...]

I was recently contacted by a reader with two very specific questions and I thought that this would be a good topic to publicity respond to. He would like to simulate his data:I have firm level data and the model is discrete choice with the main expla... [Read more...]

So I have been having difficulty getting my Stata code to look the way I want it to look when I post it to my blog.  To alleviate this condition I have written a html encoder in R.  I don't know much about html so it is likely to be ... [Read more...]

# Item equating is the practice of making the results from two # different assessments equivalent. This can be done by either# 1. having the same group take both assessments# 2. having equivalent groups take the different assessments# 3. having non-eq... [Read more...]