I have two questions regarding the useobservations command.
1. I face some problems with specifying the useobservations command correctly if I want to use only a subset of observations based upon multiple variables. If I want to combine "AND" and "OR" commands here, is the following example correct (i.e., are the brackets correct and a must)?
useobservations = variableA NE 10 AND variableB NE 1 AND variable C EQ 1 AND (variableD EQ 1 OR variableD EQ 2 variableD region EQ 4);
2. Imagine that I want to do invariance tests across 3 groups as defined by 3 different values on a specific variable although, in total, there are 5 different groups/values for this variable. Is it necessary to restrict the analysis with useobservations first to these 3 groups? Or is it enough to simply specify the 3 groups in the "grouping"?
I highly appreciate all your efforts. Thanks in advance!