osDesign: An R package for the analysis,evaluation,and design of two-phase and case-control studies

The two-phase design has recently received attention in the statistical literature as an extension to the traditional case-control study for settings where a predictor of interest is rare or subject to missclassication. despite a thorough methodological treatment and the potential for substantial eciency gains,the two-phase design has not been widely adopted. this may be due,in part,to a lack of general-purpose,readily-available soft- ware. the osdesign package for r provides a suite of functions for analyzing data from a two-phase and/or case-control design,as well as evaluating operating characteristics,including bias,eciency and power. the evaluation is simulation-based,permitting ex- ible application of the package to a broad range of scientic settings. using lung cancer mortality data from ohio,the package is illustrated with a detailed case-study in which two statistical goals are considered: (i) the evaluation of small-sample operating char- acteristics for two-phase and case-control designs and (ii) the planning and design of a future two-phase study.