On 10/30/06, Richard Johnston <[EMAIL PROTECTED]> wrote: > The confidence interval calculation in prop.test appears to be > incorrect when alternative="greater". The upper limit is always set > to 1.000. Am I missing something?
Like the t.test function the prop.test function returns a one-sided interval when the alternative is "greater" or "less". The output indicates that the 95% lower confidence bound on the proportion is 0.0369. If you choose alternative = "less" you will get a 95% upper confidence bound (and the lower bound will always be given as 0). Only when you use the default value, "two-sided", for the alternative parameter will you get both the upper and lower bounds calculated. > > total=c(250,250) > > success=c(55,31) > > prop.test(success,total,alternative="greater",correct=TRUE) > > 2-sample test for equality of proportions with continuity correction > > data: success out of total > X-squared = 7.4289, df = 1, p-value = 0.003209 > alternative hypothesis: greater > 95 percent confidence interval: > 0.03693065 1.00000000 > sample estimates: > prop 1 prop 2 > 0.220 0.124 > > > [[alternative HTML version deleted]] > > ______________________________________________ > R-help@stat.math.ethz.ch mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. > ______________________________________________ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.