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 does it mean to say that we have "90% confidence" in this interval?

A) The probability that the population mean NO_x emission μ is 0.298 is 90%.
B) The probability that the margin of error equals σ is 90%.
C) This interval was found using 90% of the data.
D) This interval was found using a procedure that produces correct results 90% of the time.