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) . A random sample of 12 cars of this particular model is taken and is found to have a mean NO_x emission of x̄= 0.298 g/mi. Government regulations call for NO_x emissions no higher than 0.3 g/mi. Do the data provide evidence that this particular model meets the government regulation? What is the test statistic for the appropriate null and alternative hypotheses?

A) z = -0.139
B) z = 0.139
C) z = 0.298
D) z = 0.445