Regions of Significance - Interaction PreviousNext
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 Jolien Van der Graaff posted on Wednesday, August 07, 2013 - 11:13 pm
I would like to know whether it's possible in MPlus to determine for a significant interaction for which regions in the range of the moderator variable, the effects of the focal predictor on the outcome variable are statistically significant, according to the Johnson-Neyman technique (Hayes & Matthes, 2009; Bauer & Curran, 2009). I found some examples of MPlus input to plot simple slopes, but in those cases you choose the values yourself (often 1 sd below and above the mean) whereas I would like to identify for which values of the moderator variable the effects of the predictor on the outcome are significant. Do you have an example of an MPlus input to do this?
Many thanks in advance for your response! Jolien
 Linda K. Muthen posted on Thursday, August 08, 2013 - 8:04 am
I think Example 3.18 will give you what you want.
 db40 posted on Tuesday, July 29, 2014 - 4:04 am
Dear Linda,

so if I wish examine the regions of significance in an interaction term using observed variables. I looked at example 3.18.

Does this appear correct. The moderators (DV1 DV2)have 4 levels each.

*SNIP*
DEFINE:
dv1PL = dv1*PL;
dv2PL = dv2*PL;

ANALYSIS:
ESTIMATOR = BAYES;
PROCESSORS = 4;
BITERATIONS = (20000);

MODEL:
y1 ON PL (b)
dv1
dv2
dv1PL
dv2PL(gamma1);


MODEL CONSTRAINT:
LOOP(mod,-2,2,0.1);
PLOT(indirect);
indirect = b*(gamma1*mod);
PLOT: TYPE = PLOT2;

OUTPUT:
TECH8;
sampstat ;
STANDARDIZED;
CINTERVAL ;
 Bengt O. Muthen posted on Tuesday, July 29, 2014 - 4:27 pm
This is not following UG ex 3.18 which has 3 slopes: b, gamma1, gamma2. Also, you say that the moderators have 4 levels each; note that your input is treating them as continuous, not categorical.
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