Re: [R] Interpreting coefficients in linear models with interaction terms

2013-01-13 Thread David Winsemius
On Jan 12, 2013, at 7:28 PM, theundergrad wrote: > 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. The number of major issues of confusion in what follows suggest that this is a topi

Re: [R] Interpreting coefficients in linear models with interaction terms

2013-01-13 Thread theundergrad
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 tw

Re: [R] Interpreting coefficients in linear models with interaction terms

2013-01-12 Thread David Winsemius
On Jan 12, 2013, at 5:00 PM, peter dalgaard wrote: On Jan 12, 2013, at 23:33 , Rolf Turner wrote: We don't do people's homework for them. But since you seem to have put in at least a little bit of your own effort . It is perfectly possible for there to be an interaction without the

Re: [R] Interpreting coefficients in linear models with interaction terms

2013-01-12 Thread peter dalgaard
On Jan 12, 2013, at 23:33 , Rolf Turner wrote: > > We don't do people's homework for them. > > But since you seem to have put in at least a little bit of your > own effort . It is perfectly possible for there to be an interaction > without there being main effects. > > Consider two factor

Re: [R] Interpreting coefficients in linear models with interaction terms

2013-01-12 Thread Rolf Turner
We don't do people's homework for them. But since you seem to have put in at least a little bit of your own effort . It is perfectly possible for there to be an interaction without there being main effects. Consider two factors A and B each with two levels. Let mu_11 be the population mea

[R] Interpreting coefficients in linear models with interaction terms

2013-01-12 Thread theundergrad
Hi, I am trying to interpret the coefficients in the model: RateOfMotorPlay ~ TestNumber + Sex + TestNumber * Sex where there are thee different tests and Sex is (obviously) binary. My results are: Residuals: Min 1Q Median 3QMax -86.90 -26.28 -7.68 22.52 123.74 Coefficients: