Message/Author 

Johnny Wu posted on Thursday, April 23, 2009  11:14 am



Hi Dr Muthen, I am conducting an LGM and want to probe for an interaction between x1 and x2 in predicting intercept and slope. I am following Preacher's advice on how to examine interactions. http://www.people.ku.edu/~preacher/interact/lca3.htm I need the asymptotic covariances for the required coefficients. Is there a way to obtain the ACOV matrix in MPLUS? Thank you very much johnnywu 


Request TECH3 in the OUTPUT command. 

Johnny Wu posted on Thursday, April 23, 2009  12:54 pm



Thank you very much. Another question: How can exogenous predictors interact with time to predict growth factors, within the LGM framework? You see, because on Preacher's website, time is treated as an predictor. Hence, a twoway interaction regressing slope on x1 with x2, would be a threeway interaction regression slope on x1 with x2 and time. How do I obtain the regression coefficient for time? 


It sounds like Preacher's approach to growth modeling is via twolevel analysis with a random slope for a time variable  see the Mplus UG example 9.16. You get the same effect by letting the x1*x2 interaction variable influence the slope growth factor in the regular Mplus singlelevel wide approach to growth: the slope growth factor multiplies time to create the product of the 3 variables. 


I have a related question. I used TECH3 to request for an asymptotic covariance matrix, but Mplus did not provide the covariance between the growth terms and the predictors. How should I proceed? Thank you Kostas 


TECH3 gives covariances among the parameter estimates. The growth factors and covariates are variables. It would be difficult to get that without changing your model. Why not regress the growth factors on the covariates. 

Fabien Long posted on Monday, January 20, 2014  3:38 am



Dear Dr. Muthen, I have a related question. I am using Preacher's online tool to graph a multilevel interaction effect (http://www.quantpsy.org/interact/hlm2.htm) and I find myself unable to find the required asymptotic covariances using the tech3 output. Elsewhere, it was stated that the order of the tech1 values can be used to interpret tech3. However, while the order of my tech1 output is Y, X1, X2, X1*X2, there is a 6*6 matrix in the tech3 output. Is there a reference that explains how to interpret the respective tech3 values? Also, does tech3 contain the covariances between the predictors and the intercept y00? Thank you for your help and your time! Fabien 


Please send the output and your license number to support@statmodel.com. 


Dr. Muthen, I am interested in the answers to the last two questions that last poster raised. Specifically, does tech3 contain the covariances between the coefficients for the predictors and the intercept? If so, where? If not, is there another way to obtain these? Also, I am unclear as to how to interpret the values in the tech3 output matrix. For instance: 0.929406D06 What does the "D06" in the above value mean? Thank you in advance for your time and help! Lauren 


Yes, Tech3 provides that information. The rows and columns are ordered according to their parameter numbers given in Tech1. As for D06, google scientific notation. For instance, 0.5D01 implies 0.05 

Claire Huang posted on Thursday, December 14, 2017  1:06 am



Dear Professor Muthen, If we sqrt the diagonal of TECH3's asymptotic covariance matrix, should the numbers equal to S.E. reported in TECH1 for each coefficient estimates? Thanks! 


Yes. 

Adam Hoffman posted on Thursday, January 25, 2018  10:29 am



Hello, I am estimating a conditional LCM and would like to the get the covariance matrix (TECH3) for the parameters in my model as I would like to probe the conditional effect on the mean factors. I understand that TECH1 provides the number labels for each of the parameters. However, I am having difficulty with the TECH1 output. The output appears to off centered and it is impossible for me to know which parameters are assigned to which number labels. Is there a simple way to know which parameters are assigned to which number labels? Thanks! 


I don't know what you mean about "off centered"  TECH1 shows the parameters in their respective parameter vectors and matrices clearly. You can send the output to Support along with your license number and point to what you don't understand. 


Dear Professors, I have specified a model with two indirect effects and am wondering: Is it possible to obtain a covariance of the estimated parameters for the indirect effects? Best regards, Christoph Schaefer 


You get that out of TECH13. But you don't need to do it that way  instead, specify the indirect effect (e.g. a*b) in the Model Constraint command and you get its SE that way. CIs can also be requested. 

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