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Chapter 2 : Statistical Considerations in Environmental Microbial Forensics

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Statistical Considerations in Environmental Microbial Forensics, Page 1 of 2

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Abstract:

Environmental microbial forensics and statistics are not always happy bedfellows. Statistical calculations are sometimes inappropriately applied, which can either give the appearance of support for a particular conclusion or fail to support an innately obvious conclusion. This is not due to any intentional deceptiveness by the scientists involved but is a reflection of issues related to dealing with sample sizes, the methodologies involved, and the difficulty of communicating uncertainties.

Citation: McBride G, Gilpin B. 2018. Statistical Considerations in Environmental Microbial Forensics, p 17-31. In Cano R, Toranzos G (ed), Environmental Microbial Forensics. ASM Press, Washington, DC. doi: 10.1128/microbiolspec.EMF-0005-2015
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Figures

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Figure 1

Power curves for a one-sample two-sided student’s test at the 5% significance level, where the population variance (σ) is unknown. Rotated numbers are the sample size ().

Citation: McBride G, Gilpin B. 2018. Statistical Considerations in Environmental Microbial Forensics, p 17-31. In Cano R, Toranzos G (ed), Environmental Microbial Forensics. ASM Press, Washington, DC. doi: 10.1128/microbiolspec.EMF-0005-2015
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Image of Figure 2
Figure 2

The value for a test positing that the true odds ratio, 1, is the sum of the areas in the left and right tails of the unit normal probability density function that are cut off by and by − (nil tests are “two-tailed”). For of 1.8 we read standard distribution tables to obtain = 2 × 0.0359 = 0.0718. (The total area under this density function is 1.) Note that larger values of give rise to smaller values of .

Citation: McBride G, Gilpin B. 2018. Statistical Considerations in Environmental Microbial Forensics, p 17-31. In Cano R, Toranzos G (ed), Environmental Microbial Forensics. ASM Press, Washington, DC. doi: 10.1128/microbiolspec.EMF-0005-2015
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References

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Tables

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TABLE 1

Example 2 × 2 contingency table

Citation: McBride G, Gilpin B. 2018. Statistical Considerations in Environmental Microbial Forensics, p 17-31. In Cano R, Toranzos G (ed), Environmental Microbial Forensics. ASM Press, Washington, DC. doi: 10.1128/microbiolspec.EMF-0005-2015
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TABLE 2

Results of nil hypothesis tests and likelihood ratio for varying sample size

Citation: McBride G, Gilpin B. 2018. Statistical Considerations in Environmental Microbial Forensics, p 17-31. In Cano R, Toranzos G (ed), Environmental Microbial Forensics. ASM Press, Washington, DC. doi: 10.1128/microbiolspec.EMF-0005-2015
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TABLE 3

O169 illnesses among Korean schoolchildren consuming kimchi (K)

Citation: McBride G, Gilpin B. 2018. Statistical Considerations in Environmental Microbial Forensics, p 17-31. In Cano R, Toranzos G (ed), Environmental Microbial Forensics. ASM Press, Washington, DC. doi: 10.1128/microbiolspec.EMF-0005-2015
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TABLE 4

Contraction of bacterial illnesses from various exposures

Citation: McBride G, Gilpin B. 2018. Statistical Considerations in Environmental Microbial Forensics, p 17-31. In Cano R, Toranzos G (ed), Environmental Microbial Forensics. ASM Press, Washington, DC. doi: 10.1128/microbiolspec.EMF-0005-2015
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TABLE 5

Campylobacteriosis cases among participants in a long-distance race

Citation: McBride G, Gilpin B. 2018. Statistical Considerations in Environmental Microbial Forensics, p 17-31. In Cano R, Toranzos G (ed), Environmental Microbial Forensics. ASM Press, Washington, DC. doi: 10.1128/microbiolspec.EMF-0005-2015

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