I am doing an 2-1-1 mediation model using Preacher's syntax. I am new to this and wonder can the '2' part of the model be a binary variable (in this case trained vs. not trained) and if so does one need to enter this as a CATEGORICAL variable? thanks
Many thanks. that is helpful. Can I please ask about sample size? I suspect you get asked this often! For the 2 variable I have two clusters (39 vs. 23). However, within clusters there are between 1 and 4 people (average about 3 per cluster). That is because the study involved project groups with maximum size 4. I have seen in a previous message that you recommend including clusters with 1 in (as long as less than 15% sample, as is this case) as it contributes to the between-subject effect. However, what are your views with such a low number per cluster?? thanks Robin
Hi Drs Muthen, Iím working with 2-1-1 models and havenít yet found any examples whereby the Within y ON m is incorporated into the total or indirect effect. Iíve been through Dr. Preacherís papers and the code on his site but could be missing something because I donít think conflation is a concern in my case. Itís meaningful for my analyses to include the Within level y ON m in the mediation model as I expect that the relationship between m and y is not the same for all cases within a cluster. I include some individual level controls that are important for the relationship of m ON x from other multilevel analyses and are as well important for y ON m. Does the following code appropriately allow for this? For context, x is a neighborhood disadvantage, m is parent substance use, y is child substance use, and the controls are family demographics. Thanks in advance!
VARIABLE: Within = m controls; Between = x mmean;
DEFINE: mmean = CLUSTER_MEAN(m); CENTER m(GROUPMEAN);
MODEL: %Within% y ON m (b2); y m ON controls;
%Between% mmean ON x (a); y on mmean (b1); y on x (c);
MODEL CONSTRAINT: NEW(IND B C TOTAL); IND = a*(b1+b2); B = b1+b2; C = c; TOTAL = (a*(b1+b2)) + c;