Some examples of research conducted in this project: Researchers often collect multivariate binary response data to compare naturally ordered experimental conditions. Some examples of ordered experimental conditions include doses in a dose-response study, cancer stages in clinical oncology, and time points in a time-course experiment. For example, the National Toxicology Program routinely conducts dose response studies to evaluate toxicity and carcinogenicity of chemicals. Typically, for each organ within each animal in the study, they record the presence and absence of tumor. Thus on each animal they obtain multivariate binary response vector where some of the components are potentially dependent. For example, mammary gland and pituitary gland tumors are known to be correlated. In such situations statistical methods that ignore the underlying dependence structure, and analyze one binary response at a time, can potentially be underpowered. In this research program we are developing multivariate statistical methods that take into account the underlying dependence structure when comparing experimental conditions. Specifically, we are developing methods for testing multivariate stochastic order among ordered experimental conditions. The new methods are not only more powerful than some of the existing methods, but they also provide biologically interpretable results. Increasingly researchers are using quantitative high throuput screening assays to screen thousands of chemicals for toxicity. In this research project we are developing statistical methods for analyzing such high dimensional data. Statistical methodologies are also being developed in this research project for analyzing data obtained from cell-cycle and circadian clock experiments as well as the human microbiome data. These new methods make use of the underlyng geometry in the data.

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Rueda, Cristina; Fernández, Miguel A; Barragán, Sandra et al. (2016) Circular piecewise regression with applications to cell-cycle data. Biometrics 72:1266-1274
Barragán, Sandra; Rueda, Cristina; Fernández, Miguel A et al. (2015) Determination of Temporal Order among the Components of an Oscillatory System. PLoS One 10:e0124842
Zhao, Haibing; Peddada, Shyamal D; Cui, Xinping (2015) Mixed directional false discovery rate control in multiple pairwise comparisons using weighted p-values. Biom J 57:144-58
Mandal, Siddhartha; Van Treuren, Will; White, Richard A et al. (2015) Analysis of composition of microbiomes: a novel method for studying microbial composition. Microb Ecol Health Dis 26:27663
Farnan, Laura; Ivanova, Anastasia; Peddada, Shyamal D (2014) Linear mixed effects models under inequality constraints with applications. PLoS One 9:e84778
Wu, Michael C; Joubert, Bonnie R; Kuan, Pei-fen et al. (2014) A systematic assessment of normalization approaches for the Infinium 450K methylation platform. Epigenetics 9:318-29
Davidov, Ori; Peddada, Shyamal (2013) Testing for the multivariate stochastic order among ordered experimental groups with application to dose-response studies. Biometrics 69:982-90
Barragán, Sandra; Fernández, Miguel A; Rueda, Cristina et al. (2013) isocir: An R Package for Constrained Inference using Isotonic Regression for Circular Data, with an Application to Cell Biology. J Stat Softw 54:
Davidov, Ori; Peddada, Shyamal (2013) The linear stochastic order and directed inference for multivariate ordered distributions. Ann Stat 41:1-40
Lim, Changwon; Sen, Pranab K; Peddada, Shyamal D (2013) Robust nonlinear regression in applications. J Indian Soc Agric Stat 67:215-234

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