The Level of Nitrogen Oxides (NO_x) in the Exhaust of Cars

Multiple Choice

The level of nitrogen oxides (NO_x) in the exhaust of cars of a particular model varies Normally, with standard deviation σ= 0.05 gram per mile (g/mi) . Government regulations call for NO_x 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 NO_x emission of 0.298 g/mi. What is a 90% confidence interval for the mean NO_x emission μ of this particular model?

A) 0.274 to 0.322 g/mi
B) 0.272 to 0.324 g/mi
C) 0.270 to 0.326 g/mi
D) 0.266 to 0.330 g/mi