Understanding Basic Statistics 6th Edition by Charles Henry Brase,Corrinne Pellillo Brase

Exercise 137

Medical: White Blood Cells Let x be a random variable that represents white blood cell count per cubic milliliter of whole blood. Assume that x has a distribution that is approximately normal, with mean = 7500 and estimated standard deviation = 1750 (See reference in problem 15). A test result of x 3500 is an indication of leukopenia. This indicates bone marrow depression that may be the result of a viral infection.
(a) What is the probability that, on a single test, x is less than 3500
(b) Suppose a doctor uses the average
for two tests taken about a week apart. What can we say about the probability distribution of
What is the probability of
3500
(c) Repeat part (b) for n = 3 tests taken a week apart.
(d) Interpretation Compare your answers to parts (a), (b), and (c). How did the probabilities change as n increased If a person had x 3500 based on three tests, what conclusion would you draw as a doctor or a nurse