Re: Correlation and Difference Scores

[James Cantor]

Where you say "interaction," I think you mean "effect."
 
If I am correctly understanding what you are trying to analyze, you are better off calculating a partial correlation: that is, calculating the correlation between patience (or volunteer experience) and the post-tutoring grades while covarying out the pre-tutoring grades.
 
- James Cantor
 

-----Original Message-----
From: SPSSX(r) Discussion [mailto:[hidden email]]On Behalf Of Shawn Hales
Sent: Monday, February 25, 2008 9:28 AM
To: [hidden email]
Subject: Correlation and Difference Scores



Hello All,

I wanting some feedback on whether the following is problematic:

I wanted to discover the interaction between the personality traits of teachers/tutors and their students success on academic measures.

I have pre-tutoring and post-tutoring grade levels from a well-normed academic test.  I created a Difference score by subtracting time 1 from time 2.  I then correlated the teacher/tutor scores from measures of "patience" and "volunteer experience" with these difference scores.

What problems could result in this set up?  Would the correlation be successful?

Shawn Hales, Psy.D.





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