Table 1 Summary of sources of error, bias parameters, and assigned distributions used in the two bias analyses
Source of potential error | Bias parameters | Assigned distributions |
|---|---|---|
Alachlor Bias Analysis | ||
number of incident cancer cases | positive predictive value negative predictive value | trapezoidal distribution with minimum = 0.95, maximum = 1.0, and modes of 0.98 and 0.99 fixed at 0.99 |
mismeasurement of cumulative exposure | cumulative exposure value assigned to each category | triangular distributions with minimum and maximum equal to reported bounds of exposure category, and mode equal to its reported midpoint |
allocation of cases to cumulative exposure categories | number of cases in each exposure category | multinomial centered on the number of cases observed in each category |
rate ratios assigned to each exposure category | log normal distribution | mean equal to the log of the reported hazard ratio for each category and variance imputed from its 95% confidence interval |
Glyphosate Bias Analysis | ||
confounding of the association by all adjustment variables | relative risk due to confounding | trapezoidal distribution with minimum of 1 (no confounding after adjustment for age), lower mode of 1.18 (bound due to confounding by education), upper mode of 1.39 (all variables but state), and maximum 1.56 (all variables, including state) |
exposure misclassification | sensitivity and specificity of exposure classification | triangular distribution with minimum 0.79, maximum 0.87, mode 0.82 based on agreement proportions |