This thesis comprises three distinct research papers. The first paper focuses on two important methodological issues pertaining to the design and analysis in a relatively new epidemiological study design, called the case-crossover design. This design, which only uses the cases, can be useful in developing hypotheses regarding the etiology of an acute event by examining the association between a recurrent exposure and the acute event. The second paper addresses model uncertainty in model-based low dose extrapolation for microbial risk assessment. Here, inference on low-dose risk estimates is...