How can I define the output membership function in Sugeno method?

Hello, I have a set of data which are not input-ouput related. I am not sure if Sugeno method could be used in this case. If so, how do I define the output membership function? Matlab FIS asks for Params value for linear type output. I realize its the co-efficients a,b,c,d from z=ax+by+cz+d that must be entered in Params box. How do I arrive at it? Is it possible to define it in the same way as the input is defined using various waveforms? I have very limited knowledge in Fuzzy. Any help is much appreciated.