Friday, February 24  
CS10 Probability Distributions 
Fri, Feb 24, 2:00 PM  3:30 PM
River Terrace 3 
Modeling Proportions and Probabilities: The Beta Distribution Is Your Friend (303366)*Paul Teetor, William Blair & Co.Keywords: proportions, beta distribution, beta regression, betabinomial model Applied statisticians often encounter proportions, probabilities, and other unitinterval data, such as failure rates and transition probabilities. It’s natural to model that data using a beta or binomial distribution, but the relevant techniques are not widely known and there are pitfalls along the way. How do we build a regression model of a beta variable? Can we adapt the binomial model when the data is overdispersed? Is the full complexity of Bayesian modeling necessary? This presentation will explain and demonstrate fitting beta and betabinomial models in practical applications. Topics will include  Review of the beta distribution  Fitting the beta distribution  Introduction to beta regression  Fitting the beta regression  Limitations of the binomial distribution, especially for overdispersed data  Advantages of the betabinomial model  Fitting the betabinomial model Examples will use real data sets, including sports data and a stockranking application. All concepts will be illustrated with R code and graphical plots.
