[R] Syntax of Levene's test
Dear All I am trying to use Levene's test (of package car), but I do not understand quite well how to use it. '?levene.test' does not unfortunately provide any example. My data are in a data frame and correspond to 4 factors plus response. Could someone please give me an example about how to use the command levene.test(y, group) ? Thanks in advance, Paul __ 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.
Re: [R] Syntax of Levene's test
Dear Paul, The argument y is the response variable and group is a factor defining groups (as ?levene.test says). If you have more than one factor, then you can use interaction() to create from them a factor with levels given by the product set of the levels of the individual factors. Here's an example library(car) data(Moore) attach(Moore) levene.test(conformity, interaction(fcategory, partner.status)) Levene's Test for Homogeneity of Variance Df F value Pr(F) group 5 1.4694 0.2219 39 levels(interaction(fcategory, partner.status)) [1] high.high low.highmedium.high high.lowlow.low [6] medium.low levels(fcategory) [1] high lowmedium levels(partner.status) [1] high low I'll add a couple of examples to the help page. I hope this helps, John John Fox Department of Sociology McMaster University Hamilton, Ontario Canada L8S 4M4 905-525-9140x23604 http://socserv.mcmaster.ca/jfox -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Paul Smith Sent: Wednesday, August 02, 2006 5:33 AM To: r-help@stat.math.ethz.ch Subject: [R] Syntax of Levene's test Dear All I am trying to use Levene's test (of package car), but I do not understand quite well how to use it. '?levene.test' does not unfortunately provide any example. My data are in a data frame and correspond to 4 factors plus response. Could someone please give me an example about how to use the command levene.test(y, group) ? Thanks in advance, Paul __ 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.
Re: [R] Syntax of Levene's test
On 8/2/06, John Fox [EMAIL PROTECTED] wrote: The argument y is the response variable and group is a factor defining groups (as ?levene.test says). If you have more than one factor, then you can use interaction() to create from them a factor with levels given by the product set of the levels of the individual factors. Here's an example library(car) data(Moore) attach(Moore) levene.test(conformity, interaction(fcategory, partner.status)) Levene's Test for Homogeneity of Variance Df F value Pr(F) group 5 1.4694 0.2219 39 levels(interaction(fcategory, partner.status)) [1] high.high low.highmedium.high high.lowlow.low [6] medium.low levels(fcategory) [1] high lowmedium levels(partner.status) [1] high low I'll add a couple of examples to the help page. Thanks, John. Now, I understand how to use levene.test. There is only a question remaining: is the null hypothesis corresponding to homogeneity of variances, i.e., should one conclude that Levene's Test for Homogeneity of Variance Df F valuePr(F) group 95 3.5919 2.2e-16 *** 864 tell us that the hypothesis that the variances are equal is (highly) significant? Paul __ 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.
Re: [R] Syntax of Levene's test
Dear Paul, Levene's test tests the null hypothesis that the variance are equal, so a small p-value suggests that they are not. Looking at your output, it seems odd that you have as many as 96 groups. John John Fox Department of Sociology McMaster University Hamilton, Ontario Canada L8S 4M4 905-525-9140x23604 http://socserv.mcmaster.ca/jfox -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Paul Smith Sent: Wednesday, August 02, 2006 5:02 PM To: r-help@stat.math.ethz.ch Subject: Re: [R] Syntax of Levene's test On 8/2/06, John Fox [EMAIL PROTECTED] wrote: The argument y is the response variable and group is a factor defining groups (as ?levene.test says). If you have more than one factor, then you can use interaction() to create from them a factor with levels given by the product set of the levels of the individual factors. Here's an example library(car) data(Moore) attach(Moore) levene.test(conformity, interaction(fcategory, partner.status)) Levene's Test for Homogeneity of Variance Df F value Pr(F) group 5 1.4694 0.2219 39 levels(interaction(fcategory, partner.status)) [1] high.high low.highmedium.high high.low low.low [6] medium.low levels(fcategory) [1] high lowmedium levels(partner.status) [1] high low I'll add a couple of examples to the help page. Thanks, John. Now, I understand how to use levene.test. There is only a question remaining: is the null hypothesis corresponding to homogeneity of variances, i.e., should one conclude that Levene's Test for Homogeneity of Variance Df F valuePr(F) group 95 3.5919 2.2e-16 *** 864 tell us that the hypothesis that the variances are equal is (highly) significant? Paul __ 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.
Re: [R] Syntax of Levene's test
On 8/3/06, John Fox [EMAIL PROTECTED] wrote: Levene's test tests the null hypothesis that the variance are equal, so a small p-value suggests that they are not. Looking at your output, it seems odd that you have as many as 96 groups. Thanks again, John. I have 4 factors with 3, 4, 4 and 2 levels (resulting in 96 groups), respectively. For each combination of the 4 factors, I have 10 observations. Paul __ 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.
