Perfluorooctanoic acid(PFOA) is a chemical used in products that coat cookware to prevent food from sticking. An agency is investigating the potential risk of PFOA as acancer-causing agent. It is known that the blood concentration of PFOA in the general population has a mean of mu equals 6

=6 parts per billion(ppb) and a standard deviation of sigma equals 10

=10 ppb. An article reported on tests for PFOA exposure conducted on a sample of 333

333 people who live near a factory that makes one such nonstick cookware product. Complete parts (a) and (b) below.

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a. What is the probability that the average blood concentration of PFOA in the sample is greater than 7.5ppb?

P(x overbar

xgreater than

>7.5)equals

=

nothing

(Round to three decimal places asneeded.)

b. The actual study resulted in x overbar

xequals

=300 ppb. Use this information to make an inference about the true mean (mu

) PFOA concentration for the population that lives near the factory.