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

Posted by Ryan on May 18, 2014; 6:15pm
URL: http://spssx-discussion.165.s1.nabble.com/Can-we-test-a-multilevel-moderation-effect-without-significant-of-the-unconditional-model-tp5726121p5726124.html

If there is apriori theory that a cross-level interaction exists between a level-1 variable and level-2 variable, then it is perfectly reasonable to immediately fit a model which includes the interaction.

That said, since the OP couldn't resist fitting both models (I'm shocked! ;-)), we might as well discuss the probable reasons for the results.

The scenario presented by the OP can likely be explained by:

1. A Type I error has been committed on the test of interaction (less likely)

or

2. A Type II error has been committed on the test of slope in the model which excluded the interaction (more likely).

Ryan

p.s. I'm fairly certain this is discussed in one of the widely used and cited multilevel textbooks but I can't recall which one at the moment.

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