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Experiment ID
140
Pathogen
Cryptosporidium hominis
Cryptosporidium parvum
Agent Strain
TAMU isolate
Contains Preferred Model
Yes
Reference
Messner, M. J., Chappell, C. L., & Okhuysen, P. C. (2001). Risk Assessment for Cryptosporidium: A Hierarchical Bayesian Analysis of Human Dose Response Data. Water Research, 35, 16. Retrieved from https://www.sciencedirect.com/science/article/pii/S0043135401001191
Exposure Route
oral
Response
infection
Host type
human
# of Doses
4.00
Dose Units
oocysts
Μodel
exponential
k
5.72E-02
LD50/ID50
1.21E+01
Description
TAMU data 
Dose Infected Non-infected Total
10 2 1 3
30 2 1 3
100 3 0 3
500 5 0 5

 

Goodness of fit and model selection
Model Deviance Δ Degrees 
of freedom		 χ20.95,1 
p-value 		χ20.95,m-k 
p-value
Exponential 1.07 0.21 3 3.84 
0.647 		7.81 
0.783
Beta Poisson 0.864 2 5.99 
0.649
Exponential is preferred to beta-Poisson; cannot reject good fit for exponential.

 

Optimized k parameter for the exponential model, from 10000 bootstrap iterations
Parameter MLE estimate Percentiles
0.5% 2.5% 5% 95% 97.5% 99.5%
k 5.72E-02 1.80E-02 1.92E-02 2.46E-02 2.65E+00 2.65E+00 2.65E+00
ID50/LD50/ETC* 1.21E+01 2.61E-01 2.61E-01 2.61E-01 2.82E+01 3.61E+01 3.84E+01
*Not a parameter of the exponential model; however, it facilitates comparison with other models.

Exponential model plot, with confidence bounds around optimized model

Parameter histogram for exponential model (uncertainty of the parameter)

 

 

References

  • Messner, M. J., Chappell, C. L., & Okhuysen, P. C. (2001). Risk Assessment for Cryptosporidium: A Hierarchical Bayesian Analysis of Human Dose Response Data. Water Research, 35, 16. Retrieved from https://www.sciencedirect.com/science/article/pii/S0043135401001191