求助Mplus问题。
已经用SPSS分组了，80组，一组3个数据。还是报错。
INPUT INSTRUCTIONS  
TITLE: this is multilevel regression, m y are level 2, x is level 1   
DATA: FILE IS 1.dat;   
VARIABLE: NAMES ARE id a1-a5 b1-b4 c1-c3;    USEVARIABLE = id x m y;   
DEFINE: x = sum(a1-a5);         
m= sum(b1-b4);         
y=sum(c1-c3);  
WITHIN = m y;  
BETWEEN = x;  
MISSING = blank;  
CLUSTER = id;  
ANALYSIS: TYPE = TWOLEVEL RANDOM;  MODEL:   
%WITHIN%          s | y ON m;          %BETWEEN%          s ON x;  
OUTPUT:  TECH8 SAMPSTAT;

*** ERROR in VARIABLE command  TYPE=TWOLEVEL requires specification for the CLUSTER option.