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Statistical Thinking for Forensic Practitioners Short Course – Session 3

Session 3 of this three-part CSAFE short course was held on April 23, 2021.

Presenter:

Hal Stern
Provost and Executive Vice Chancellor, Chancellor’s Professor, University of California, Irvine
CSAFE Co-Director

Presentation Description:

The National Academies report in 2009 and the PCAST report in 2016 encouraged consideration of quantitative approaches to assessing forensic evidence. In this session, we review two of the most often-suggested quantitative approaches, the two-stage approach and the likelihood ratio (Bayes factor) approach. Specific topics include:

  • The two-stage approach to assessing forensic evidence
    • The role of statistical tests in assessing the similarity of two samples
    • Approaches for assessing the relevance of observed similarities
  • Introduction to the likelihood ratio approach
    • Definition and interpretation of the likelihood ratio/Bayes factor
    • Possible applications to different types of evidence (DNA, trace, pattern)
    • Score-based likelihood ratios
    • Sensitivity of the likelihood ratio to modeling choices
  • Results of studies comparing different ways of expressing source conclusions

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