Model-fitting in the presence of outliers

We study the problem of parametric model-fitting in a finite alphabet setting. We characterize the weak convergence of the goodness-of-fit statistic with respect to an exponential family when the observations are drawn from some alternate distribution. We then study the effects of outliers on the model-fitting procedure by specializing our results to ∈-contaminated versions of distributions from the exponential family. We characterize the sensitivity of various distributions from the exponential family to outliers, and provide guidelines for choosing thresholds for a goodness-of-fit test that is robust to outliers in the data.