contrast (orthogonal) coding with unequal cell frequencies

Posted by Sidra on Oct 19, 2016; 3:10am
URL: http://spssx-discussion.165.s1.nabble.com/contrast-orthogonal-coding-with-unequal-cell-frequencies-tp5733307.html

Hi Friends,
 I made a post on this forum a few days back relating to use of categorical variables in multiple regression analysis. I was suggested to create contrast groups to overcome the issue I was facing. I have created two contrast variables for a categorical variable with three levels.

Variable levels/categories are:
1-single,  2-married/widowed/divorced- with children,  3-married/widowed/divorced- without children

 I created following two contrast variables(as I was suggested)

category levels      single       mwd-having children          mwd-without children


Contrast 1              -2                +1                              +1

Contrast 2               0                +1                               -1
 
Now the issue is while I was brushing up on my knowledge of contrast coding, I read that categories/levels with unequal size (n) should be adjusted by multiplying each code with the number of observations for the corresponding cell. But  I'm not really sure how to do it exactly and even after I have done it, how to make sure that I did it rightly.  I searched for a query similar to mine posted here and I found the one  given below but unfortunately the question has not been answered by anyone.
The frequencies for each cell are as follows: single= 65, Married/widowed/divorced-having children= 50, Married/widowed/divorced-without children= 19
I need your suggestions.

http://spssx-discussion.1045642.n5.nabble.com/orthogonal-coding-with-unequal-n-tp1076217.html