Hi, I have very limited (one class and the rest self-taught) statistics background (I am a comparative biology major) working on an independent study. I think that I am beginning to understand:
The coefficient SexM is the slope estimate for TestNumber1. If I add the coefficients for the other two interaction terms to the coefficient of SexM, I will get the slope estimate for the other two tests. How would I quantify the significance of the interaction and SexM in the model? If, as I have done previously and as David suggests, I look at three different models each using only one test, I can quantify the effect of SexM simply by looking at the associated p-value. If, however, I chose to look at the interaction model in order to reduce the number of tests conducted , I do not have one number to look at that quantifies the significance of sex or the interaction. I thought about doing two F-tests, one comparing this model to a model without interaction (to find the significance of the interaction) and one comparing this model to one with only TestNumber (to find the total significance of sex). When I do this, I get a p-value of 0.006 for the first test and 0.3 for the second. My understanding of this is that SexM is non-significant; however, the relationship between SexM and RateOfMotorPlay significantly changes with TestNumber. This seems strange to me, but I seem to be hearing that it is possible. If this is true, I think that reporting that sex is non-significant is adequate and I do not need to report anything about the interaction since my research question is related to the effect of sex, not the change in the effect of sex over time. Does this approach adequately address the issue of whether or not sex is related to RateOfMotorPlay? Thank you all so much for you helpful responces -- View this message in context: http://r.789695.n4.nabble.com/Interpreting-coefficients-in-linear-models-with-interaction-terms-tp4655365p4655390.html Sent from the R help mailing list archive at Nabble.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.
