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 μ = 6900 and
estimated standard deviation σ = 2150. 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? (Round your answer to four decimal places.)
(b) Suppose a doctor uses the average x for two tests taken
about a week apart. What can we say about the probability
distribution of x?
The probability distribution of x is approximately normal with
μx = 6900 and σx = 1520.28.
The probability distribution of x is approximately normal with
μx = 6900 and σx = 2150.
The probability distribution of x is not normal.
The probability distribution of x is approximately normal with
μx = 6900 and σx = 1075.00.
What is the probability of x < 3500? (Round your answer to
four decimal places.)
(c) Repeat part (b) for n = 3 tests taken a week apart. (Round
your answer to four decimal places.)
(d) Compare your answers to parts (a), (b), and (c). How did
the probabilities change as n increased?
The probabilities decreased as n increased.
The probabilities increased as n increased.
The probabilities stayed the same as n increased.
If a person had x < 3500 based on three tests, what
conclusion would you draw as a doctor or a nurse?
It would be a common event for a person to have two or three
tests below 3,500 purely by chance. The person probably does not
have leukopenia.
It would be an extremely rare event for a person to have two
or three tests below 3,500 purely by chance. The person probably
has leukopenia.
It would be an extremely rare event for a person to have two
or three tests below 3,500 purely by chance. The person probably
does not have leukopenia.
It would be a common event for a person to have two or three
tests below 3,500 purely by chance. The person probably has
leukopenia.