I want to estimate the volatility of a variable which I already estimate with proc model. I know that I can save my variable and calculate its volatility with proc means but I want to estimate its volatility in proc model to test for its equality with another variable.

I try to do that to test for the equality of standard deviation of variables A and B.

test std(A)=std(B);

but it does not work. I have this message.

ERROR: The function STD requires at least 2 arguments. There are too few arguments for the

function STD.