A certain assay for serum alanine aminotransfer ase (ALT) is rather imprecise. The results of repeated assays of a single specimen follow a normal distribution with mean equal to the ALT concentration for that spec-men and standard deviation equal to 4 U/l (as in Exercise 4.S.15). Suppose a hospital lab measures many specimens every day, and specimens with reported ALT alues of 40 or more are flagged as "unusually high." If a patient's true ALT concentration is 35 U/l, find the probability that his specimen will be flagged as "unusually high"
(a) If the reported value is the result of a single assay.
(b) If the reported value is the mean of three independent assays of the same specimen.