1.  wider

2.  predict.qeLin()

3.  

library(regtools)
mlb <- mlb[,4:5] 
z <- qePolyLin(mlb,'Weight',holdout=NULL) 
print(predict(z,77.2))  # 218.2192

4.  

sim <- fction(n,nreps) {
   tmp <- replicate(nreps,
      {
          x <- rexp(n,1/2)
          s2 <- var(x) * (n-1) / n
          sqrt(s2)
      }
   )
   mean(tmp)
}

print(sim(1000,10000))  # 1.99948