Question

Estimating Car Pollution: In a sample of seven cars, each car was tested for nitrogen oxide emissions (in grams per mile) and the following results were obtained: 0.06, 0.11, 0.16, 0.15, 0.14, 0.08, 0.15 (based on data from the Environmental Protection agency).

a) Assuming that this sample is representative of the cars in use, construct a 99% confidence interval estimate of the mean amount of nitrogen-oxide emissions for all cars.

b) If the Environmental Protection Agency requires that nitrogen-oxide emissions be less than 0.165 grams/mile, can we safely conclude that this requirement is being met?

Answer 1

First we need to find the mean and standard deviation of the sample. Following table shows the calculations:

	X	(X-mean)^2
	0.06	0.00376996
	0.11	0.00012996
	0.16	0.00148996
	0.15	0.00081796
	0.14	0.00034596
	0.08	0.00171396
	0.15	0.00081796
Total	0.85	0.00908572

Sample size:

n= 7

The sample mean is

The sample standard deviation is

Assumption: Population is normally distributed.

(b)

We cannot say that all cars meet the EPA requirement because confidence interval contains 0.165 g /mi.