刚学sem在用amos

总是提示我这个问题，怎么改都不行，高手老手帮看看
An error occurred while attempting to fit the model.
In order to analyse data with missing observations,you must explicity estimate means and intercepts.
In Amos Graphics,place acheck mark next to "Estimate means and intercepts"in the "Analysis Properties" window.
In programming the Amos engine,use the ModelMeansAndIntercepts method.
还有这个The model is probably unidentified. In order to achieve identifiability, it will probably be necessary to impose 1 additional constraint.

非常感谢