# 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.

• 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

• Statistics -

Long form:

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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