Re: [Freesurfer] comparing models

2014-03-04 Thread jorge luis
Hi Eric The longitudinal lme model is no different from cross-sectional models when it comes to testing the significance of a covariate. You just simply use an F-test with the contrast [0 0 0 0 0 1] to test the last covariate in the first model. You can then drop the last covariate if the test is

Re: [Freesurfer] comparing models

2014-03-04 Thread Eric Cunningham
Sorry! I made a mistake with my example. I meant to say group_effect instead of rand_effect. It should read as follows: Y1 = B1 + B2(time) + B3(group_effect1) + B4(group_effect*time) + B5(covariate_1) +B6(covariate_2) Y2 = B1 + B2(time) + B3(group_effect1) + B4(group_effect*time) + B5(covariate_1

[Freesurfer] comparing models

2014-03-04 Thread Eric Cunningham
Hello Freesurfer experts, I have a question about how to determine if a covariate is important in a mixed effects model for example: Y1 = B1 + B2(time) + B3(rand_effect1) + B4(rand_effect*time) + B5(covariate_1) +B6(covariate_2) Y2 = B1 + B2(time) + B3(rand_effect1) + B4(rand_effect*time) + B5(cov