Research Interests: Probability Models and Statistical Inference Estimation Theory, Probability, Stochastic Processes, Mathematical Learning Models, Biological Models, Characterizations, Income Distributions, Order Statistics, Inequality Measurement, Record Values, Conditionally Specified Distributions, Bayesian Inference, Multivariate Distributions. Dr. Arnold is also interested in distributional characterizations with special emphasis on their utility for checking on model adequacy or feasibility using classical or Bayesian techniques.