You don't need to test that the _sample_ variances are different: They already are. Statistical tests of hypotheses are not about sample statistics, but distributional charateristics.
It seems to me that reinforcement of some basic stat concept may do you quite a bit of good. If you don't have the basics, you're just going to get more and more puzzled every step of the way. Just a frank suggestion. Best, Andy From: Daren Tan > > I am testing whether the sample variances are equal. When > p-value < 0.05 (alpha), should accept null hypothesis (sample > variances are equal) or reject it ? > > > The two new examples with each having same sample variances > also puzzle me. Why are the p-values different ? > > bartlett.test(rep(rnorm(5),times=4), rep(1:5, each=4)) > > > Bartlett test of homogeneity of variances > > > data: rep(rnorm(5), times = 4) and rep(1:5, each = 4) > Bartlett's K-squared = 0.8681, df = 4, p-value = 0.929 > > > bartlett.test(rep(rnorm(5),times=4), rep(1:5, each=4)) > > > Bartlett test of homogeneity of variances > > > data: rep(rnorm(5), times = 4) and rep(1:5, each = 4) > Bartlett's K-squared = 3.5599, df = 4, p-value = 0.4688 > > > > From: [EMAIL PROTECTED] > > To: [EMAIL PROTECTED]; [EMAIL PROTECTED] > > Date: Fri, 22 Aug 2008 11:25:36 -0400 > > Subject: RE: [R] Test of Homogeneity of Variances > > > > What are your hypotheses? Once you state what they are, > interpretation should be straightforward. > > > > > > > > -----Original Message----- > > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Daren Tan > > Sent: Friday, August 22, 2008 11:18 AM > > To: [EMAIL PROTECTED] > > Subject: [R] Test of Homogeneity of Variances > > > > > > I am testing the homogeneity of variances via bartlett.test > and fligner.test. Using the following example, how should I > interpret the p-value in order to accept or reject the null > hypothesis ? > > > > set.seed(5) > > x <- rnorm(20) > > bartlett.test(x, rep(1:5, each=4)) > > > > > > Bartlett test of homogeneity of variances > > > > > > data: x and rep(1:5, each = 4) > > Bartlett's K-squared = 1.7709, df = 4, p-value = 0.7778 > > > > fligner.test(x, rep(1:5, each=4)) > > > > Fligner-Killeen test of homogeneity of variances > > > > > > data: x and rep(1:5, each = 4) > > Fligner-Killeen:med chi-squared = 1.0819, df = 4, p-value = 0.8971 > > > > ______________________________________________ > > 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. > > This email message, including any attachments, is for > ...{{dropped:6}} > > ______________________________________________ > 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. > Notice: This e-mail message, together with any attachme...{{dropped:12}} ______________________________________________ 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.
