Re: Can we test a multilevel moderation effect without significant τ of the unconditional model?

Posted by Bruce Weaver on May 18, 2014; 1:40pm
URL: http://spssx-discussion.165.s1.nabble.com/Can-we-test-a-multilevel-moderation-effect-without-significant-of-the-unconditional-model-tp5726121p5726123.html

I don't profess extraordinary expertise in HLM, but I'll jump in with a question and a comment.

Which book are you looking at, and what exactly does it say?  

Now the comment:  Given that you appear to have an a priori interest in that particular cross-level interaction, my gut feeling is that you should go ahead and look at it regardless of significance (or not) of the variance of the random slopes.  I see a parallel here to going ahead with planned orthogonal contrasts (in the ANOVA context) regardless of the significance of the omnibus F-test.  

There...maybe that will provoke the real HLM experts (Ryan, Alex...) to jump in with their comments.  ;-)

凌楚定 wrote

Hello list,
 
Is there anyone here who is expert in HLM? I have a basic question:
 
I am attempting to test a multilevel moderation model, in which the independent and dependent variables are at level 1, while the moderator is at level 2. According to what I learned from the textbook previously, I should run the unconditional model firstly to examine whether the variance component (τ) of the dependent variable’s slope is significant. Unfortunately, it was not significant. It seems that it is not necessary for me to test further. However, I am curious about the result so I did the multilevel moderation test and found it was significant.
 
Now here comes my question: Maybe it is inconsistent with the principle of HLM to test such a moderation test, but how to explain the significant moderation effects since I got the statistic results?
 
I would be grateful if any of you can give me some hopeful suggestions.
 


Chu-Ding LING
Ph.D. Student of Business Administration
School of Management
Zhejiang University