Exercise 1335 Blood potassium level continued Judys measured

Exercise 13.35 Blood potassium level, continued. Judy’s measured potassium level varies according to the Normal distribution with with =3.8 and =0.2mmol/l. Let’s consider what could happen if we took 4 separate measurements from Judy. What is the blood potassium level L such that the probability is only 0.05 that the average of 4 measurements is less than L? (Hint: This requires a backward Normal calculation.)

the book says about 3.64 but i got 3.28

Solution