odds.ratio {HH}R Documentation

Calculate or plot the odds ratio for a 2x2 table of counts.

Description

Calculate or plot the odds ratio for a 2x2 table of counts. The plot shows the confidence intervals on the probability of row2 for fixed odds ratio and specified probability for row1.

Usage

odds.ratio(x, alpha = 0.05)

plot.odds.ratio(x,
 ylab = "prob(col1 | row1)", xlab = "prob(col1 | row2)",
 alpha = c(0.05, 0.5),
 legend.x=1.05,
 oma=c(0,0,0,5), ...)

Arguments

x 2 x 2 table of counts
alpha Significance levels of test. odds.ratio requires a single number in the range [0,1]. plot.odds.ratio accepts more than one number on the range [0,1] and draws confidence lines at each value.
xlab, ylab x- and y-labels for the plot. Sensible defaults are generated.
... other arguments, currently ignored.
legend.x x position of left-hand side of legend.
oma outer margin par()$oma, needed to make room for legend.

Value

plot.odds.ratio draws a plot and invisibly returns the same list as odds.ratio for the first value of alpha. odds.ratio returns the list:

p1, p2 proportion of each row total observed in the first column.
omega1, omega2 odds for each row, p/(1-p)
psihat odds ratio, omega2/omega1
s.ln.psihat standard deviation of ln(psihat)
ci.ln.psihat confidence interval for ln(psihat) using normal approximation
ci.psihat confidence interval for psihat calculated ase p(ci.ln.psihat)
prob1 seq(0,1,.05), set of p1 values for plotting.
odds1 p1/(1-p1)
odds2 odds for the second row needed to retain psihat with the specified odds1, calculated as odds1*psihat.
ci.odds2 confidence interval for odds2
prob2 odds2 / (odds2+1)
ci.prob2 ci.odds2 / (ci.odds2+1)

Author(s)

Richard M. Heiberger <rmh@temple.edu>

References

Heiberger, Richard~M. and Holland, Burt (2004b). Statistical Analysis and Data Display: An Intermediate Course with Examples in S-Plus, R, and SAS. Springer Texts in Statistics. Springer. ISBN 0-387-40270-5.

Examples

glasses <- read.table(hh("datasets/glasses.dat"), header=FALSE)

glasses <- matrix(unlist(glasses),
                  nrow=2,
                  dimnames=list(
                    c("glasses","no.glasses"),
                    c("delinq","non.del")))

## draw the iso-odds ratio plot with 50% CI and 95% CI,
## invisibly return the 95% CI
plot.odds.ratio(glasses)

[Package HH version 2.1-25 Index]