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Statistical Considerations in Environmental Microbial Forensics.
Graham McBride1, Brent Gilpin2
1National Institute of Water & Atmospheric Research (NIWA), Hamilton, Hamilton, 3216 New Zealand.
Microbiology Spectrum
|October 12, 2016
Summary
Statistical methods in environmental microbial forensics require careful application. This review highlights likelihood ratios as superior evidence metrics and Bayesian methods for attribution probabilities, emphasizing clarity on prior assumptions.
Area of Science:
- Environmental microbial forensics
- Statistical analysis in scientific investigations
Background:
- Statistical calculations are often misapplied in environmental microbial forensics.
- Issues arise from sample sizes, methodologies, and uncertainty communication.
Purpose of the Study:
- To illustrate methods for minimizing statistical problems in environmental microbial forensics.
- To examine the use of genotyping in food, water, and disease investigations.
Main Methods:
- Exploration of P values as evidence metrics.
- Quantification of evidence value.
- Conversion of evidence value to attribution probabilities using Bayesian methods.
Main Results:
- P values can detect trivial effects with large sample sizes.
- Likelihood ratios are recommended as a strength-of-evidence metric.
- Bayesian methods can calculate attribution probabilities, but priors can be subjective.
Conclusions:
- Likelihood ratios provide a robust measure of evidence.
- Bayesian analysis is suitable for attribution probabilities in legal contexts, requiring transparent prior assumptions.
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