@article{JSSv048i09, title={Bradley-Terry Models in R: The BradleyTerry2 Package}, volume={48}, url={https://www.jstatsoft.org/index.php/jss/article/view/v048i09}, doi={10.18637/jss.v048.i09}, abstract={This is a short overview of the R add-on package BradleyTerry2, which facilitates the specification and fitting of Bradley-Terry logit, probit or cauchit models to paircomparison data. Included are the standard ‘unstructured’ Bradley-Terry model, structured versions in which the parameters are related through a linear predictor to explanatory variables, and the possibility of an order or ‘home advantage’ effect or other ‘contest-specific’ effects. Model fitting is either by maximum likelihood, by penalized quasi-likelihood (for models which involve a random effect), or by bias-reduced maximum likelihood in which the first-order asymptotic bias of parameter estimates is eliminated. Also provided are a simple and efficient approach to handling missing covariate data, and suitably-defined residuals for diagnostic checking of the linear predictor.}, number={9}, journal={Journal of Statistical Software}, author={Turner, Heather and Firth, David}, year={2012}, pages={1–21} }