Message/Author 


Hello Prof. Muthen A clarification on usage of Model Test in multigroup analysis.I have two groups, and trying to check if the regression parameter with label a is equal to parameter b. When I ran the code Model test: a = b waldchi sq test is nonsignificant Wald Test of Parameter Constraints Value 0.981 Degrees of Freedom 1 PValue 0.3219 However if use Model test: a  b = 0 the results are Wald Test of Parameter Constraints Value 7.280 Degrees of Freedom 1 PValue 0.0070 I thought in both ways am testing the same difference in parameter test. Please help 


I have a question similar to the previous poster. I'm doing a multiple group analysis and I want to test the noninvariance of a particular path coefficient. Do I need to label the coefficient in the overall model command? My input is below: MODEL: st BY svs1svs8; scientid by atmr sdcr sciid; tapp BY newagq1 newagq4 newagq7; sapp by newagq2 newagq5 newagq8; tapp on scientid st; sapp on scientid st; scientid on st; MODEL INDIRECT: tapp ind scientid st; sapp ind scientid st; Model other: scientid on st(a); Model science: scientid on st(b); Model test: a=b; Eric 


The way you label them is correct. Model test should have 0 = ab; 


Thanks so much, Bengt. Eric 

Aidan posted on Monday, May 11, 2015  8:37 am



Dear Bengt, I have run a multigroup latent growth model and am trying to compare the two groups for significant differences in the mean and variance of the two latent factors. Using the code below (I have also tested an alternative form of the MODEL TEST command, where p1=p21, and so on) produces a Wald test with a very low, significant, pvalue for the omnibus test of all four parameters. However, when I examine each parameter onebyone, none of them show a significant difference between groups. Model Group 1: [int] (p1); [slope] (p2); int (p3); slope (p4); Model Group 2: [int] (p21); [slope] (p22); int (p23); slope (p24); Model test: 0 = p1p21; 0 = p2p22; 0 = p3p23; 0 = p4p24; Can you tell me if I am doing anything wrong? It seems odd that none of the individual parameters are close to significance while the omnibus test is significant  I am not sure how one would report this in a useful fashion, since no specific difference between the two groups can be identified. I have searched the forum archives for an answer, but haven't seen this described before  apologies if I have overlooked anything. Thank you. 


The joint test has more power to reject than each individual test so the outcome is quite possible. You can try to use a likelihoodratio chi2 difference test instead of the Wald test to check if you get the same result. 

Pia H. posted on Thursday, October 06, 2016  1:02 am



Dear Prof Muthén I want to compare regression coefficients of latent (interaction) variables between two groups using the model test command, but I get an error message in my output: ANALYSIS: TYPE = COMPLEX MIXTURE RANDOM; ITERATIONS = 5000; PROCESSORS = 8; model = nocovariances; ALGORITHM=INTEGRATION; INTEGRATION = MONTECARLO (5000); CHOLESKY = OFF; MCONVERGENCE = .01; MODEL: %OVERALL% (input omitted) g_PSYCHO on g_TRAUMA (a); g_PSYCHO ON age_cen (c); g_TRAUMA ON age_cen (e); agextrauma age_cen XWITH g_TRAUMA; g_PSYCHO ON agextrauma (g); %MAOA#2% g_PSYCHO on g_TRAUMA (b); g_PSYCHO ON age_cen (d); g_TRAUMA ON age_cen (f); g_PSYCHO ON agextrauma (h); Model test: 0=ab; 0=cd; 0=ef; 0=gh; *** ERROR in MODEL command Random effect variables can only be declared in the OVERALL model. Thank you! Best, Pia 


We need to see the full output  send to Support along with your license number. 

Qiong Wu posted on Thursday, June 15, 2017  9:41 pm



Dear Bengt, I'd like to follow up with the discussion where you suggested "The joint test has more power to reject than each individual test so the outcome is quite possible. You can try to use a likelihoodratio chi2 difference test instead of the Wald test to check if you get the same result." I am testing the difference of mediation between two groups. The joint test had more power than individual tests about a1b11  a2b12, a1b21  a2b22. What is the syntax to use a likelihoodratio chi2 difference test instead of the Wald test? MODEL constraint: new(a1b11 a1b21 a2b12 a2b22); a1b11=a1*b11; a1b21=a1*b21; a2b12=a2*b12; a2b22=a2*b22; Model test: 0 = a1b11  a2b12; 0 = a1b21  a2b22; 


The likelihoodratio chi2 test is obtained from 2 runs. One run with equality and one without. 

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