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Statistics

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The level of nitrogen oxides (NOX) in the exhaust of a particular car model varies with mean 0.9 grams per mile and standard deviation 0.15 grams per mile .

(a) What sample size is needed so that the standard deviation of the sampling distribution is 0.01 grams per mile ?

  • Statistics - ,

    Never mind, got it. If anyone wants to know how to get it though...

    1.5/(sq root of .9)=.01

    Solve the equation, then square each side.

    Answer=225

  • Statistics - ,

    And by .9 I definitely meant n.....haha

  • Statistics - ,

    That is a brutal solution lol

  • Statistics - ,

    Solve what equation? You didn't post an associated equation. and 1.5/sqrt of 0.9 does not equal .01

    Then square what? Elaborate please.

  • Statistics - ,

    Long form:

    start with:
    0.15 / (square root of n) = 0.01

    multiply both sides by (square root of n) which gives you:
    0.15 = (0.01) x (square root of n)

    divide both sides by 0.01 which gives you:
    0.15 / 0.01 = square root of n

    both sides to the power of 2:
    (0.15 / 0.01)^2 = (square root of n)^2
    0.0225 / 0.0001= n
    n = 225

    Short form:

    n = (0.15)^2 / (0.01)^2
    n = 0.0225 / 0.0001
    n = 225

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