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  • Dec 9, 2011, 10:09 AM
    wyattkendra
    Stats homework problem -- percentage
    Assume that the average annual salary for a worker in the United States is $28,500 and that the annual salaries for Americans are normally distributed with a standard deviation equal to $6,250. Find the following:
    (A) What percentage of Americans earn below $18,000?
    (B) What percentage of Americans earn above $41,000?

    Please show all of your work.
  • Dec 13, 2011, 04:48 AM
    Unknown008
    Define your variable first.

    This is a normal distribution with mean 28,000 and standard deviation 6,250. Let X be the salary of a worker.

    X ~ N(28000, 6250^2)

    To get the percentage of Americans who earn below $18,000, take X < 18000.

    Then use your z-table to find P(X < 18000), which would map onto:



    You use the same principle with the next part.

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