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help > RE: How to use "age" as covariates?
Apr 19, 2015 07:04 PM | Alfonso Nieto-Castanon - Boston University
RE: How to use "age" as covariates?
Hi Jeff,
Typically the regression coefficient value(s) (or a linear combination of them defined by your between-subjects contrast) will be listed as 'beta=###' in Tools.Calculator. So, for example in a group by age model, if you select 'groupA' 'groupB' 'ageA' and 'ageB', and enter a contrast eye(4) (or [1 0 0 0; 0 1 0 0; 0 0 1 0; 0 0 0 1]), you will see something like 'beta=[1;2;3;4]'. Those will be the four regression coefficients of your second-level model (one coefficient for each subject-effect entered). That means that the estimated regression equations would be:
connectivity = 1 + 3*age (for group A)
connectivity = 2 + 4*age (for group B)
(changing 1- 4 to the actual listed values)
note: you could have similarly entered a [1 0 0 0] contrast to get just the '1' value, a [0 1 0 0] contrast to get the '2' value, etc. Entering the eye(4) contrast simply gets you the four values faster...
Hope this helps
Alfonso
Originally posted by Jeff Browndyke:
Typically the regression coefficient value(s) (or a linear combination of them defined by your between-subjects contrast) will be listed as 'beta=###' in Tools.Calculator. So, for example in a group by age model, if you select 'groupA' 'groupB' 'ageA' and 'ageB', and enter a contrast eye(4) (or [1 0 0 0; 0 1 0 0; 0 0 1 0; 0 0 0 1]), you will see something like 'beta=[1;2;3;4]'. Those will be the four regression coefficients of your second-level model (one coefficient for each subject-effect entered). That means that the estimated regression equations would be:
connectivity = 1 + 3*age (for group A)
connectivity = 2 + 4*age (for group B)
(changing 1- 4 to the actual listed values)
note: you could have similarly entered a [1 0 0 0] contrast to get just the '1' value, a [0 1 0 0] contrast to get the '2' value, etc. Entering the eye(4) contrast simply gets you the four values faster...
Hope this helps
Alfonso
Originally posted by Jeff Browndyke:
This is a great and very helpful thread.
Once one obtains output plots in Tools/Calculator with r2 and significance values, where can the resulting regression formula be found or constructed (e.g., y-intercept)? I'd like to include those with the analysis output plots.
Thanks,
Jeff
Once one obtains output plots in Tools/Calculator with r2 and significance values, where can the resulting regression formula be found or constructed (e.g., y-intercept)? I'd like to include those with the analysis output plots.
Thanks,
Jeff