HH (version 2.1-23)

odds.ratio: 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)

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)