nulldata 100
scalar n = $nobs

# generate n observations on x   
series x = uniform()
# set a seed if you want to get same results each time you run this
set seed 3213799
# Set the values of the parameters
scalar slope = .5  # regression slope
scalar sigma = 10 # measurement error in y
scalar n = $nobs

# start the loop, indicating the desired number of samples.
loop 400 --progressive --quiet
   series u = normal(0,sigma) 
   # generate sample of x and y 
   series ystar=20+slope*x+u
   series y = (ystar>20) 
   genr prop = mean(y)
   series y=y*ystar
 
ols y const x
tobit y const x
print prop
endloop