Carcinogenic Effects of a Fungicide
Data from Gart (1971) on the carcinogenic effects of a certain fungicide
in two strains of mice.
Of interest is how the association between group (Control, Treated)
and outcome (Tumor, No Tumor) varies with sex and
strain of the mice.
Breslow (1976) used this data to illustrate the application of linear models to log odds ratios.
data(Fungicide)
The data comprise a set of four 2 x 2 tables classifying 403 mice, either Control or Treated and whether or not a tumor was later observed. The four groups represent the combinations of sex and strain of mice. The format is: num [1:2, 1:2, 1:2, 1:2] 5 4 74 12 3 2 84 14 10 4 ... - attr(*, "dimnames")=List of 4 ..$ group : chr [1:2] "Control" "Treated" ..$ outcome: chr [1:2] "Tumor" "NoTumor" ..$ sex : chr [1:2] "M" "F" ..$ strain : chr [1:2] "1" "2"
All tables have some small cells, so a continuity correction is recommended.
Gart, J. J. (1971). The comparison of proportions: a review of significance tests, confidence intervals and adjustments for stratification. International Statistical Review, 39, 148-169.
Brewlow, N. (1976), Regression analysis of the log odds ratio: A method for retrospective studies, Biometrics, 32(3), 409-416.
data(Fungicide)
# loddsratio was moved to vcd; requires vcd_1.3-3+
## Not run:
if (require(vcd)) {
fung.lor <- loddsratio(Fungicide, correct=TRUE)
fung.lor
confint(fung.lor)
}
## End(Not run)
# visualize odds ratios in fourfold plots
cotabplot(Fungicide, panel=cotab_fourfold)
# -- fourfold() requires vcd >= 1.2-10
fourfold(Fungicide, p_adjust_method="none")Please choose more modern alternatives, such as Google Chrome or Mozilla Firefox.