Hello all, I am about to send off a manuscript and, although I am fairly confident I have used the lme function correctly, I want to be 100% sure. Could some kind soul out there put my mind at ease?
I am simply interested in whether a predictor (SPI) is related to height. However, there are five different populations, and each may differ in mean level of height as well as the relationship between SPI and height. Thus, I also want to a) account for mean level differences in height and b) check whether the relationship between height and SPI is different between the groups. I hope this is sufficient information. height, SPI, covariate1, and covariate2 are numeric. population is a factor with 5 levels. Here are the steps I took: summary(mod1 <- lme(height ~ SPI + covariate1 + covariate2, random = ~ SPI | population)) summary(mod2 <- lme(height ~ SPI + covariate1 + covariate2, random = ~ 1 | population)) anova(mod1,mod2) #this checks whether there is evidence for IQ & SPI being related differently between the 5 populations. Is this correct? THANKS! Matt -- Matthew C Keller Asst. Professor of Psychology University of Colorado at Boulder www.matthewckeller.com ______________________________________________ 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.
