 Usage:  {b,s,cv} = tobit(x,y)  
 
 Input:

  x                      n x d matrix , the observed explanatory variable 
                         
  y                      n x 1 matrix , the observed response variable 
                         
 Output:

  b                      d x 1 vector, contains the estimated coefficients of the components of x 
                         
  s                      scalar, contains the estimated standard deviation of the error term 
                         
  cv                     (d+1)x(d+1) matrix, estimated covariance matrix for [b,s] 
                         
--------------------------------------------------------------
(C) MD*TECH Method and Data Technologies, 17.8.2000
