Question

1)The level of nitrogen oxides (NOX) in the exhaust of cars of a particular model varies Normally with standard deviation σ=0.05 grams per mile (g/mi). Government regulations call for NOX emissions no higher than 0.3 g/mi. A random sample of 12 cars of this particular model is taken and is found to have a mean NOX emission of 0.298 g/mi. What is a 90% confidence interval for the mean NOX emission μ of this particular model?

Group of answer choices

0.272 to 0.324 g/mi

0.274 to 0.322 g/mi

0.266 to 0.330 g/mi

0.270 to 0.326 g/mi

2)The level of nitrogen oxides (NOX) in the exhaust of cars of a particular model varies Normally with standard deviation σ=0.05 grams per mile (g/mi). Government regulations call for NOX emissions no higher than 0.3 g/mi. A random sample of 12 cars of this particular model is taken and is found to have a mean NOX emission of 0.298 g/mi. What does it mean to say that we have "90% confidence" in this interval?

Group of answer choices

The probability that the population mean NOX emission mu is 0.298 is 90%.

This interval was found using a procedure that produces correct results 90% of the time.

The probability that the margin of error equals sigma is 90%.

This interval was found using 90% of the data.

Answer 1

1)

Standard error of mean = = 0.05 / = 0.01443376

Z score for 90% confidence interval is 1.645

Lower limit of 90% confidence interval = 0.298 - 1.645 * 0.01443376 = 0.274 g/mi

Upper limit of 90% confidence interval = 0.298 + 1.645 * 0.01443376 = 0.322 g/mi

0.274 to 0.322 g/mi

2)

We have "90% confidence" in this interval means that

This interval was found using a procedure that produces correct results 90% of the time.