On Tue, 2007-10-09 at 18:37 -0400, Wayne Aldo Gavioli wrote: > > Hello all, > > I have to run a 2 Sample Confidence Interval on some data; the command for > such > intervals is "confint(...)", but in the help documentation it says that you > need a "fitted model object" in order to run this command. What does that > mean? > > The data is very small, it's: > > x=c(8,12,10,14,2,0,0) > y=c(-6,0,1,2,-3,-4,2) > > > and I want to be able to run a Confidence interval for the difference of two > means (x-bar minus y-bar). Do I have to fit these two pieces of data into > some > kind of object? > > > A little confused,
Try this, presuming that your data above are not paired: > t.test(x, y) Welch Two Sample t-test data: x and y t = 3.0621, df = 9.264, p-value = 0.01308 alternative hypothesis: true difference in means is not equal to 0 95 percent confidence interval: 2.039893 13.388678 sample estimates: mean of x mean of y 6.571429 -1.142857 See ?t.test for more information. confint(), as per the top of help page which you were reading: "Computes confidence intervals for one or more parameters in a fitted model." Said differently, it computes confidence intervals for the coefficients in a linear model, not for the difference in means in a two sample test. HTH, Marc Schwartz ______________________________________________ R-help@r-project.org 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.