text: Therefore, we find the Rao-Blackwell éstimator formula_6 After doing some algebra we have formula_7 Since the average number "X"1+ ... + "X""n" of calls arriving during the first "n" minutes is "n"λ, one might not be surprised if this éstimator has a fairly high probability (if "n" is big) of being close to formula_8 So δ1 is cléarly a very much improved éstimator of