Mahima Hada posted on Monday, August 23, 2010 - 11:46 am
I am estimating a two-level model. I want to test hypotheses that the total effect of one variable is greater than the other (testing for trade-offs). I am using MODEL TEST to run Wald Tests, but the test results don't match with my graphed results. I am wondering if I am using the wald test appropriately. Would appreciate your help (Mplus ver 6). Code:
In MODEL TEST, I don't see that the specification shows a greater then relationship. I don't see any indication that sf=1. And I don't think the total effect is the sum of two regression coefficients.
Mahima Hada posted on Monday, August 23, 2010 - 2:15 pm
1) I tried a "greater than" relationship test and got the error message that I cannot use <or> in model test. Hence, the equality test as a first step. And then I figured I can calculate the correct p-value for a one-sided test.
2) SF is manipulated as 0 or 1. 0 is the base, so including hm1_sf includes the effect of Hm on the DV when sf=1.
3)Thanks for the third point - this is where I am struggling with calculating the effect using wald tests. I want to test that when sf=1, what is more important Rep or Hm for my sample. Say, Y= b0 + b1*Rep + b2*Rep*sf + b3*Hm + b4*Hm*sf
then for calculating relative effects for the wald tets: dY/dRep = b1 + b2 dY/dHm = b3 + b4
hence my equations.
Appreciate your advice. thanks.
Mahima posted on Monday, August 23, 2010 - 4:48 pm
I think I figured out the problem. The below specification of the test gives results that make sense substantively. Add adding random effects, intercepts etc. does not change the result: