Yes, though you might want to demean age before computing the quadratic.
doug
On 02/24/2014 10:13 AM, Yang, Daniel wrote:
Hi FreeSurfer Experts,
With age as a continuous variable, qdec can test the linear effect of
age. To test the quadratic effect of age, do I just create a
curvilinear term like age*age and add into the existing equation?
For example:
original equation: Y = intercept + age + Factor + age*Factor
new equation: Y = intercept + age + Factor + age*Factor + age*age +
age*age*Factor
Best,
Daniel
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Daniel (Yung-Jui) Yang, Ph.D.
Postdoctoral Researcher
Yale Child Study Center
New Haven, CT
Tel: (203) 737-5454
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MGH-NMR Center
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