大家好!小弟在用mplus做多水平模型时运行结果出错显示如下，希望大家能够帮我解决一下谢谢：
  DATA:FILE IS 11.dat;
  VARIABLE:NAMES ARE A X Y Z M;
  CLUSTER=A;
  WITHIN=X M;
  BETWEEN=Z;
  ANALYSIS:TYPE=TWOLEVEL;
  MODEL:
  %WITHIN%
  Y ON X M;
  %BETWEEN%
  Y ON Z;
  OUTPUT:STDYX TECH1;
*** ERROR
  One or more between-level variables have variation within a cluster for
  one or more clusters.  Check your data and format statement.
     Between    Cluster ID with variation in this variable
     Variable     (only one cluster ID will be listed)