Andrew Li posted on Monday, February 13, 2017 - 2:13 pm
Hello, I am trying to interpret the interaction of two L-2 variables in the prediction of a L-1 variable. In this case, X and W are L-2 variables and Y is a L-1 Variable. I hypothesize that the cross-level relationship between X and Y will be moderated by W. I have the codes below. In particular, I am not sure the last few lines with respect to simple slope analyses are correct. Would you please take a look? BTW, all the variables are continuous variables and I have grandmean centered the two level-2 variables. Thank you.
usevariables = a1 x w y inter ; cluster = a1; between = x w inter; define: center x w (grandmean); inter = x * w; analysis: type = twolevel; model: %between% y on x (b1) w (b2) inter (b3); model constraint: new (x1 x2 x3); x1 = b1 + b3*(1); x2 = b1; x3 = b1 + b3*(-1); output: Sampstat stdyx;
Andrew Li posted on Tuesday, February 14, 2017 - 7:02 am
Dear Dr. Muthen, Thank you so much for your reply. I use the Mplus code from the Geiser book (p. 216). In the demonstration of the codes for the Mean-as-outcomes model (a model where there is no L-1 predictor but one L-2 predictor), the code does not include a %within line. I wonder why this line is included as you suggested. Is it because now I have more than one L-2 predictor and also the interaction between two L-2 predictors? Thank you.
Make sure that the within-level variance is estimated - check your output. If it isn't, add it.
Andrew Li posted on Wednesday, February 15, 2017 - 5:03 pm
Dear Dr. Muthen, Thank you for your response. I really appreciate it. You mention variance in your response. I use Tech3 to get the variance/covariance matrix. However, I don't quite understand the numbering on the x and y axes. I know that I can get the info with Tech1 in the output. The problem is I have a really hard time figuring out which number matches which parameter. I am sure there is a very intuitive way but I guess it gets lost in me. I read the relevant section in the manual and I still have no clues. Your help is greatly appreciate.
TECH1 gives a number to each free parameter in the model. Those numbers are used in the TECH3 variance/covariance matrix. For example the 1,1 entry is the variance of parameter 1. The 1,2 entry is the covariance between parameter 1 and parameter 2 etc.
Andrew Li posted on Thursday, February 16, 2017 - 7:23 am
Dear Dr. Muthen, Thank you for your response. I understood the variance/covariance matrix in the TECH3 output. The problem I have is related to the TECH1 output. Specifically, I don't know which parameter is related to which number. The TECH1 output includes a lot of symbols like beta, alpha, etc. I don't know how each number corresponds to the specific variables/parameters in my model. Andrew