vcdExtra (version 0.5-2)

Fungicide: Carcinogenic Effects of a Fungicide

Description

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.

Usage

data(Fungicide)

format

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"

source

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.

Details

All tables have some small cells, so a continuity correction is recommended.

References

Brewlow, N. (1976), Regression analysis of the log odds ratio: A method for retrospective studies, Biometrics, 32(3), 409-416.

Examples

data(Fungicide)
fung.lor <- loddsratio(Fungicide, correct=TRUE)
fung.lor
confint(fung.lor)

# visualize odds ratios in fourfold plots
cotabplot(Fungicide, panel=cotab_fourfold)
#  -- fourfold() requires vcd >= 1.2-10
fourfold(Fungicide, p_adjust_method="none")