rm(list=ls())
x = sample(1:500, 50, replace = FALSE)
a = 5
b = -6
b_hat = 0
a_hat = 0
run = 40
for(i in 1:run){
  y = a + b*x + rnorm(50)
  b_hat[i] = cov(x,y)/var(x);b_hat
  a_hat[i] = mean(y) - b_hat[i]*mean(x)
}
plot(b_hat)
abline(h = -6)