Two-sample test for independent proportions The application prop.test in R outputs the chi square statistic as the test statistic along with the confidence interval for the difference. The data should be provided as a matrix with 2 columns giving the counts of successes and failures, respectively. tab1=matrix(c(3,9, 22,16),nc=2) prop.test(tab1, correct=TRUE)

Gives something like this:

2-sample test for equality of proportions with continuity correction data: tab1 X-squared = 2.7412, df = 1, p-value = 0.09779 alternative hypothesis: two.sided 95 percent confidence interval: -0.50722061 0.02722061 sample estimates: prop 1 prop 2 0.12 0.36