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help > RE: ANCOVA rank deficient
Aug 22, 2016 04:08 AM | Andrew Zalesky
RE: ANCOVA rank deficient
Hi Juan,
this is just like a typical F-test: you may want to perform subsequent testing to identify the groups that are driving the result. This can be done using independent t-tests, as you suggest, although there are more fancy ways of doing this.
To test the significance of a single covariate, use a t-test and set the contrast vector equal to 1 in the position corresponding to the covariate. All other elements in the contrast vector should be zero. This will give you the significance of the covariate.
Andrew
Originally posted by Juan Pablo Princich:
this is just like a typical F-test: you may want to perform subsequent testing to identify the groups that are driving the result. This can be done using independent t-tests, as you suggest, although there are more fancy ways of doing this.
To test the significance of a single covariate, use a t-test and set the contrast vector equal to 1 in the position corresponding to the covariate. All other elements in the contrast vector should be zero. This will give you the significance of the covariate.
Andrew
Originally posted by Juan Pablo Princich:
Dear Andrew and Giulia
Thanks for the example , it is very useful.
Still have two questions maybe not related to NBS but to statistics in general that you could please kindly acknowledge...
1. under this ancova example , do we need to perform a multiple comparison correction if we perform any additional ttest on the same matrices but with a different group definition ? in other words i found a significant network with this design but also want to look for differences re-arranging a sub group distribution according to clinical properties.. lets say i split the patients group in two and compare them with individual t test using the same design agaisnt all the controls.
2. is there a way to define a contrast that only shows the effect of covariates alone? (not accounting for the groups differences) or shall i modify the design matrix ?
Thanks for your patience and grateful help!
sincerely, Juan P
Thanks for the example , it is very useful.
Still have two questions maybe not related to NBS but to statistics in general that you could please kindly acknowledge...
1. under this ancova example , do we need to perform a multiple comparison correction if we perform any additional ttest on the same matrices but with a different group definition ? in other words i found a significant network with this design but also want to look for differences re-arranging a sub group distribution according to clinical properties.. lets say i split the patients group in two and compare them with individual t test using the same design agaisnt all the controls.
2. is there a way to define a contrast that only shows the effect of covariates alone? (not accounting for the groups differences) or shall i modify the design matrix ?
Thanks for your patience and grateful help!
sincerely, Juan P
Threaded View
| Title | Author | Date |
|---|---|---|
| Giulia Forcellini | May 11, 2016 | |
| Andrew Zalesky | May 12, 2016 | |
| Juan Pablo Princich | Dec 7, 2017 | |
| Andrew Zalesky | Dec 7, 2017 | |
| Juan Pablo Princich | Dec 13, 2017 | |
| Juan Pablo Princich | Dec 18, 2017 | |
| Juan Pablo Princich | Aug 20, 2016 | |
| Andrew Zalesky | Aug 22, 2016 | |