 Usage:  {simexl,simexq} = simex(y, w, z, su2, lam, b)  
 
 Input:

  y                      n x 1 matrix, the design variables 
                         
  w                      n x 1 matrix, surrogate variable of unobservable variable 
                         
  z                      n x 1 matrix, covariate measured without error 
                         
  su2                    the variance of the measurement error 
                         
  lam                    pseudo-parameter for generating pseudo-errors 
                         
  b                      the number of replication in each simulation 
                         
 Output:

  simexl                 the estimate based on linear extrapolant function 
                         
  simexq                 the estimate based on quadratic extrapolant function 
                         
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(C) MD*TECH Method and Data Technologies, 17.8.2000
