Regression

[jdykstra]

Hello,

I was just curious if there is a difference between a*b and a(b) in proc glm.

proc glm;
      class a b;
      model y=a b a*b;
run;

proc glm;
      class a b;
      model y=a b a(b);
run;

[ballardw]

a(b) is "a nested within b"

a*b is interaction

make some data, run the code, see the result. Make sure to use some variety in the a b values per record