16 Using the truncated normal distribution for Bayes factors in hierarchical model selection.

Oregon Convention Center 

In the identification of source problems within forensic science, the forensic examiner is tasked with providing a summary of evidence to allow a decision maker to evaluate the source of some evidence. The type of data encountered in the forensic identification of source problems often has a hierarchical structure, where there is a within and between source distribution for each object in a sample. One method of providing this summary of evidence is through a likelihood ratio (LR) or a Bayes factor (BF). With these methods, it is often the case that the two densities are estimated separately and then the ratio is reported, which can lead to instances where the resulting LR is large due to a small density in the denominator. In this work, we explore the use of the truncated normal distribution for use in LRs and BFs to attempt to alleviate this phenomenon. We also begin to characterize the robustness of these truncated normal LR methods.

forensic source identification

value of evidence

likelihood ratio

truncated normal distribution 

Section on Bayesian Statistical Science