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 ? = 6300 and estimated standard deviation ? = 1650. 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.)
1

(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 ? x = 6300 and ? x = 825.00. the probability distribution of x is not normal. the probability distribution of x is approximately normal with ? x = 6300 and ? x = 1650. the probability distribution of x is approximately normal with ? x = 6300 and ? x = 1166.73.

what is the probability of x < 3500? (round your answer to four decimal places.)
3

(c) repeat part (b) for n = 3 tests taken a week apart. (round your answer to four decimal places.)
4

(d) compare your answers to parts (a), (b), and (c). how did the probabilities change as n increased?
the probabilities increased as n increased. the probabilities stayed the same as n increased. the probabilities decreased 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 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 has 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 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.