Inferential Methods for Quantile Regression

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While least squares regression targets the conditional mean function in a regression model, quantile regression provides more complete information on the conditional distribution of the response variable. It is especially valuable when there is heteroscedasticity or general heterogeneity in the population. To facilitate quantile regression modelling in a wider areas of applications, this proposal aims to develop inferential procedures for quantile regression models to account for the presence of random-effects or random censoring in the observations. Although random-effects and censoring have been well studied under linear models equipped with parametric, and often Gaussian, likelihoods, the conventional inference procedures do not have straightforward extensions to the quantile regression model when standard minimal assumptions are made on the conditional distributions. The principle investigator aims to make focused attempts in developing new ideas and tools to make possible appropriate inference in quantile regression models with random-effects or with censoring. The proposed research will build upon the recent developments in quantile regression modelling and incorporate some innovative ideas to develop appropriate inferential methods that are mathematically justified, mainly through large sample theory, and statistically meaningful at realistic sample sizes. Currently available methods for statistical inference in quantile regression models are not well-developed to handle random-effects or random censoring. For example, the analysis of GeneChip data in genomics would result in inflated false discovery rates without taking the array effect as random. The proposed research will develop new methods that preserve statistical confidence in a wider range of quantile regression based applications. The PI will pursue collaboration with other scientists to ensure that the methodologies under development are valuable to researchers in the biological sciences, health sciences, engineering, economics, and finance. The proposed activities will also involve training of graduate students for future researchers in statistics as well as providing selected undergraduate students with research experience.