Message/Author 

Sara Suzuki posted on Tuesday, September 18, 2018  1:27 am



What is a correct interpretation of the BCH procedure if I run the following syntax? It is different to the results without the covariates, but I am not sure how to interpret. USEVARIABLES ARE ind1 ind2 ind3 ind4 ind5 ind6 ind7 ind8 covariate1 covariate2; AUXILIARY = (BCH) distal1 distal2 distal3; MISSING ARE ALL (88, 777, 999); CLASS = C(3); ANALYSIS: TYPE = MIXTURE; MODEL: %OVERALL% C on covariate1 covariate2; 


The interpretation is the same as the one without the covariates. The results are different because the latent class solution is different. You should be able to see the differences between the latent classes not just in the BCH variables but in the actual model as well. You can consider running the manual BCH see Section 3 https://www.statmodel.com/examples/webnotes/webnote21.pdf where you can use the covariates and the distal outcomes in the auxiliary model. 

Sara Suzuki posted on Wednesday, September 19, 2018  10:36 am



Hello Dr. Asparouhov, Thank you for your reply. If I follow the steps outlined in Section 3 of Webnote 21, and run the below models, will this give me a BCH result that is "controlled for" by the covariates? I want to know: after controlling for the influence of the covariates on class assignment, how are classes related to the distal outcome? Step 1: USEVARIABLES ARE ind1 ind2 ind3 ind4 ind5 ind6 ind7 ind8; AUXILIARY = covariate1 covariate2 distal1 distal2 distal3; MISSING ARE ALL (88, 777, 999); CLASS = C(3); ANALYSIS: TYPE = MIXTURE; SAVEDATA: FILE=manualBCH.dat; SAVE=bchweights; Step 2: DATA: FILE=manualBCH.dat; USEVARIABLES ARE covariate1 covariate2 distal1 distal2 distal3 w1w3; TRAINING = w1w3(BCH); MISSING ARE ALL (88, 777, 999); CLASS = C(3); ANALYSIS: TYPE = MIXTURE; MODEL: %OVERALL% C ON X; 


You need to also say "Y ON X" in your model  see the scripts in the webnote. 

Sara Suzuki posted on Wednesday, September 19, 2018  9:00 pm



Hello Dr. Muthén, Since I do not want to regress my distal on the covariates, so I should not leave out "Y on X"? 

Sara Suzuki posted on Wednesday, September 19, 2018  9:00 pm



I meant to say: Since I do not want to regress my distal on the covariates, should I not leave out "Y on X"? 


Yes, you should. 

Sara Suzuki posted on Thursday, September 20, 2018  8:30 pm



Ok  great so I will run the model without "Y on X." Thank you Dr. Muthén. 

Sara Suzuki posted on Sunday, September 30, 2018  4:31 am



I tried both regressing the distal on covariates (syntax A) and not regressing the distal on covariates (syntax B) and got very different Wald test results depending on what I did. Could you help me understand which model is better? Is it correct that syntax A, where I regress the distal on covariates as well, gives a more "pure" Wald test, showing whether the means of the distal differ between classes after accounting for selection into classes based on covariates and effect of covariates on the distals? Syntax A: DATA: FILE=manualBCH.dat; USEVARIABLES ARE covariate1 covariate2 distal1 distal2 distal3 w1w3; TRAINING = w1w3(BCH); CLASS = C(3); ANALYSIS: TYPE = MIXTURE; MODEL: %OVERALL% C ON covariate1 covariate2; distal1 distal2 distal3 ON covariate1 covariate2; %C#1% distal1 distal2 distal3 ON covariate1 covariate2; %C#2% distal1 distal2 distal3 ON covariate1 covariate2; %C#3% distal1 distal2 distal3 ON covariate1 covariate2; Syntax B: DATA: FILE=manualBCH.dat; USEVARIABLES ARE covariate1 covariate2 distal1 distal2 distal3 w1w3; TRAINING = w1w3(BCH); CLASS = C(3); ANALYSIS: TYPE = MIXTURE; MODEL: %OVERALL% C ON covariate1 covariate2; 


You are right about syntax A  it is better when there are direct effects. 

Scot Seitz posted on Saturday, December 14, 2019  12:25 pm



I recently ran the third step of the BCH method. My auxiliary model has multiple covariates (both dichotomous and continuous) and 3 continuous outcomes. I am trying to examine the role of the covariates in predicting the latent classes. In the output in the "Categorical Latent Variables" section, I see that each class is regressed on each covariate (comparing each class to the last class, which seems to be the reference class). I have a few questions: 1) How can I change the reference class so that I can examine the role of each covariate between different classes? 2) Are the estimates in the "Categorical Latent Variables" section regression coefficients? 3) In the "Categorical Latent Variables" section, can I obtain standardized estimates? I included "output: stdyx" in my syntax and standardized results are not reported for this section (although standardized results are reported for other sections). 4) Do you suggest any other way to examine the role of the covariates in predicting the latent classes in the third step of the BCH method? 


1. Reorder the weights like this training=w1 w2 w4 w3(bch); 2. It is multinomial logistic regression https://en.wikipedia.org/wiki/Multinomial_logistic_regression 3. I would recommend using define: standardize x; so the "model results" will be standardized. 4. You can use the 3step (R3step option) and the 1step estimation. If those estimates disagree you might have direct effects from the covariate to the latent class variable indicators. See Table 4 http://www.statmodel.com/download/3stepOct28.pdf 

shonnslc posted on Sunday, May 10, 2020  1:17 pm



Hi, I am trying the manual BCH method to examine if profiles differ in a distal outcome. I know how to do that in an automatic way, but not sure how to do that in a manual way: usevar= y BCHW1 BCHW2 ; CLASSES = c(2); training=BCHW1 BCHW2 (bch); Analysis: Type = mixture; starts = 0; model: %overall% %c#1% [y]; %c#2% [y]; This will only give me the mean of the distance outcome in each class, but how can I get the differences between them. Thank you! 


Use Model Constraint. %c#1% [y] (y1mean); %c#2% [y] (y2mean); Model constraint: new(diff); diff= y1mean  y2mean; 

shonnslc posted on Thursday, May 14, 2020  8:45 am



Thank you, Muthen. But isn't this approach (using the model constraint command) based on the Wald test instead of the chisquare test used in the automatic approach? Does that matter? Thank you! 


No, the Wald test is used in Model Tests. Model Constraint uses a regular ztest for each New parameter. 

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