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Crissy
Crissy asked in Science & MathematicsMathematics · 1 decade ago

Choosing an Appropriate Sample Size?

A union of restaurant and foodservice workers would like to estimate the mean hourly wage,u , of foodservice workers in the U.S. The union will choose a random sample of wages and then estimate u using the mean of the sample. What is the minimum sample size needed in order for the union to be 90% confident that its estimate is within $0.45 of u? Suppose that the standard deviation of wages of foodservice workers in the U.S. is about $2.25.

Carry your intermediate computations to at least three decimal places. Write your answer as a whole number (and make sure that it is the minimum whole number that satisfies the requirements).

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  • cidyah
    Lv 7
    1 decade ago
    Favorite Answer

    Sample size = [z sd / error]^2

    z (for a 90% confidence interval is) is 1.645.

    sd = 2.25

    error = 0.45

    Sample size = [ (1.645)(2.25) /0.45]^2 = (8.225)^2 = 67.650625

    = 68 samples

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