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help > RE: How to define "site" as covariate
Dec 23, 2022 01:12 AM | Alfonso Nieto-Castanon - Boston University
RE: How to define "site" as covariate
Hi Alex,
While that approach is fine for two sites (or when controlling for the effect of a categorical factor with two levels), for three or more sites the appropriate control will involve defining one covariate per site, each with 0/1 values indicating which subjects come from each individual site. Using instead as a control a variable with values 1,2,3 will only control for sorted effects across those three sites, leaving other potential inter-site differences uncontrolled.
Best
Alfonso
Originally posted by Alexandra Muratore:
While that approach is fine for two sites (or when controlling for the effect of a categorical factor with two levels), for three or more sites the appropriate control will involve defining one covariate per site, each with 0/1 values indicating which subjects come from each individual site. Using instead as a control a variable with values 1,2,3 will only control for sorted effects across those three sites, leaving other potential inter-site differences uncontrolled.
Best
Alfonso
Originally posted by Alexandra Muratore:
Hi Alfonso,
Is this different than creating a variable called "site" with 3 levels (1,2,3), and including that as a covariate of no interesT?
Thank you,
Alex
Is this different than creating a variable called "site" with 3 levels (1,2,3), and including that as a covariate of no interesT?
Thank you,
Alex
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