Search Algorithms: MIMBuild |
Introduction
MIM Build stands for Multiple Indicator Model Build. It is one of the three algorithms in Tetrad designed to build pure measurement/structural models (the others are the Build Pure Clusters algorithm and the Purify algorithm).
MIM Build should be used to learn causal relationships among latent variables in a when the measurement model is given in advance but the structural model is unknown.
The MIM Build algorithm also assumes that the underlying (unknown) data generating process is a linear graph. If the user strongly suspects that the latents or indicators may be non-linearly related, MIM Build should not be used. We are also assuming that latents here do not have other hidden common causes.
All observed variables are assumed to be continuous, and therefore the current implementation of the algorithm accepts only continuous data sets as input. For general information about model building algorithms, consult the Search Algorithms page.
Create a new Search object as described in the Search Algorithms page, but in order to follow this tutorial, use the following graph to generate a simulated continuous data set:
When the MIM Build algorithm is chosen from the Search box, a window
appears for specifying search parameters.
The parameters that are used by MIM Build can be specified in this window. The parameters are as follows:
In this example, we want to enter the measurement model that we know is the correct one by assumption. In other words, variables X1, X2 and X3 should be clustered together, since they are pure indicators of a same latent. Variables X4, X5 and X6 form another cluster, and the same holds for X7, X8 and X9. In order to perform cluster assignment, since click the respective combo box and choose the cluster that shows up in the list. For example, click the X4 combo box and choose Cluster 1. Do the same for X5 and X6. For variables X7, X8 and X9, choose Cluster 2. The final outcome should be as follows:
Execute the search as explained in the Search Algorithms page.
MIM Build returns a pattern over latent
variables that is completely analogous to the one produced by a PC Search, or GES Search. The
same interpretation used in such algorithms can be applied to MIM Build
output.