he level of nitrogen oxides (NOX) in the exhaust of a particular car model varies with mean 0.7 grams per mile and standard deviation 0.19 grams per mile .
(a) What sample size is needed so that the standard deviation of the sampling distribution is 0.01 grams per mile ?
2 answers
1.21 Gijawatts!!!
Long form:
0.19 / (square root of n) = 0.01
multiply both sides by (square root of n) which gives you:
0.19 = (0.01) x (square root of n)
divide both sides by 0.01 which gives you:
0.19 / 0.01 = square root of n
both sides to the power of 2:
(0.19 / 0.01)^2 = (square root of n)^2
0.0361 / 0.0001= n
n = 361
Short form:
n = (0.19)^2 / (0.01)^2
n = 0.0361 / 0.0001
n = 361
Therefore the sample size that is needed is 361.
0.19 / (square root of n) = 0.01
multiply both sides by (square root of n) which gives you:
0.19 = (0.01) x (square root of n)
divide both sides by 0.01 which gives you:
0.19 / 0.01 = square root of n
both sides to the power of 2:
(0.19 / 0.01)^2 = (square root of n)^2
0.0361 / 0.0001= n
n = 361
Short form:
n = (0.19)^2 / (0.01)^2
n = 0.0361 / 0.0001
n = 361
Therefore the sample size that is needed is 361.
2 answers