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Re: contrast (orthogonal) coding with unequal cell frequencies

Posted by Kirill Orlov on Oct 20, 2016; 4:36pm
URL: http://spssx-discussion.165.s1.nabble.com/contrast-orthogonal-coding-with-unequal-cell-frequencies-tp5733307p5733343.html

Are you speaking in your initial question about contrast coefficients (coefficients in a contrast, they sum to zero) or contrast coding (values of contrast variables)? See http://stats.stackexchange.com/a/221868/3277


20.10.2016 19:07, Sidra пишет:
I'm sorry fellows, I do not have a background of statistics ..that's why I'm
having a hard time understanding your suggestions here. Perhaps I need to be
a little bot more comprehensive.
 
I have IVs of nursing specialty,  qualification, age, years of experience,
work shift, marital status and childberaing status; independent variable
being perceived stress by nurses. I need to see the effect of nursing
specialty (as main variable of interest) on perceived stress while
controlled for confounders. 
I will identify confounders by noting crude coefficient of nursing specialty
and then noticing the change in its coefficient when each IV is placed in
the model with nursing specialty (one variable at a time). If adding a
variable in regression model brings a change of more than 10% in coefficient
of nursing specialty, I ll treat that variable as a confounder. Since to
find out if a variable is a confounder, I have to put that confounder alone
along with nursing specialty in regression model, I am not sure if I can
treat contrast 1 and contrast 2 (in place of marital status and childbearing
status) as individual variables to see how much change each brings about in
the coefficient of nursing specialty separately.

I hope I have made myself sufficiently clear. Please bear with me and offer
your kind insight on this problem.


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