oddsratio.estimation {epitools}R Documentation

Odds ratio estimation and with Fisher's exact test

Description

Estimates odds ratio using different methods and performs Fisher's exact test for testing the null of independence of rows and columns in a contingency table with fixed marginals.

Usage

oddsratio.crude(...)
oddsratio.fisher(...)
oddsratio.ss(...)

Arguments

... A 2x2 table or equivalent. See as.epitable for details.

Details

These functions calculate the odds ratio using different methods and performs Fisher's exact test for testing the null of independence of rows and columns in a contingency table with fixed marginals. These functions calculate the odds ratio for the following type of 2x2 contingency table (opposite of how data is displayed in epidemiology textbooks, but consistent with how data is handled in statistical programs):

                Outcome
   Exposure     No  Yes
     No (ref)    a    b
     Yes         c    d

The oddsratio.crude function calculates the odds ratio using the cross-product (a*d)/(b*c).

The oddsratio.fisher function calculates the odds ratio using the fisher.test function. The odds ratio differs slightly from the crude calculation.

The oddsratio.ss function calculates the odds ratio using a small sample (ss) adjustment (Jewell 2004): (a*d)/((b+1)*(c+1)).

Value

$data original data
$proportion.exposed proportion exposed for each outcome category
$estimate odds ratio
$fishers.exact p value

Note

Visit http://www.epitools.net for the latest.

Author(s)

Tomas Aragon, aragon@berkeley.edu, http://www.medepi.net/aragon

References

Nicholas P. Jewell (2004), Statistics for Epidemiology, Chapman & Hall, 1st Edition

See Also

See also riskratio.estimation, as.epitable, epitab

Examples

##From Jewell (2004), p. 79
oddsratio.crude(88, 20, 555, 347)
oddsratio.fisher(88, 20, 555, 347)
oddsratio.ss(88, 20, 555, 347)

dat <- matrix(c(88, 20, 555, 347), 2, 2, byrow = TRUE)
dimnames(dat) <- list (c("0", ">=1"), c("Controls", "Cases"))
names(dimnames(dat)) <- c("Coffed drinking (cups/day)", "Pancreatic Cancer")
dat
oddsratio.crude(dat)
oddsratio.fisher(dat)
oddsratio.ss(dat)

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