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Prof. Muthen, I have the following model to estimate Y2, Y3, Y4 = g(eta1) (g is a vector function) eta1 = h(X2) Y1 = f(X1, eta1) Where eta1 is a continuous latent variable and Y2, Y3, Y4 are ordinal indicators capturing eta1. Y1 is BINARY and the variable of primary interest. X’s are exogenous variables. We have sample selection issue. I was wondering whether it would be OK to use IMR (inverse mills ratio) as one of the explanatory variable in Y1 equation and then use WLSMV. I am calculating IMR from the selection model; Z = z(X4) Could you kindly suggest me some related references? Thanking you. |
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This sounds like a reasonable approach. You may want to model the heteroscedasticity of your y1 residuals. |
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Thank you Madam. Checking heteroscedasticity in equation Y1 is in fact a good idea. Could you kindly suggest me an example to handle heteroscedasticity using MPlus. Regards |
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I can think of 2 approaches that could be useful. One draws on UG ex3.9. The other draws on UG ex5.3 with CONSTRAINT = x, where the heteroscedasticity is a function of the covariate x. But you would have to explore. |
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Dear Prof. Muthen, I have a simple question. I would like to select only some groups of the sample from the main dataset and save it for another analysis. Please could you advise what command that I can use. Thanks. |
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You can select observations using the USEOBSERVATIONS option of the VARIABLE command. If you want to save that data set, use the FILE option of the SAVEDATA command. |
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Dear Linda, Thanks for the advise. I had tried this but the saved file contained no data. Please suggest. Here is the command. DATA: File is C:\mplus\batch1.dat Variable: names are ...(I have all the variables in the dataset written here including w1 which is used in useobservation command)...; Useobservation = w1 EQ 1; Savedata: File is C:\mplus\w1; I got the file out of the run but there is no data in the file. It is supposed to be about 600 observations here. Thanks. |
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Please send the relevant files and your license number to support@statmodel.com. |
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I am interested in using the NOBSERVATIONS option to select a subset (N) of a simulated dataset. The manual indicates that the first N cases in the dataset would be selected. Is it possible to select a random sample of cases using the NOBSERVATIONS option? If all else fails I can create randomized groups the dataset and use the USEOBSERVATIONS option, but this does not seem any more appealing (to me) than just using the first N cases (in this case). Thank you for any clarification/assistance. |
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Mplus does not have an option for random sampling from a data set. You would need to do that outside of Mplus. |
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Thank you for your quick response. |
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