Travel and Transportation The Boeing 747-8 is a technologically advanced aircraft with a new wing design and GEnx-2B engines, and is capable of holding more passengers and payload than previous versions of the 747. In addition, this plane has better fuel efficiency than the 747-400 and the A380, which means lower carbon emissions.
A random sample of twelve 747-8 test flights was obtained and the carbon emission was measured on each (in grams CO2 per seat-km). The sample mean was 72. Assume the carbon emission distribution is normal and σ = 8.7.
a. Find a 99% confidence interval for the true mean carbon emission of all 747-8 planes.
b. The carbon emission for the A380 is 80 g CO2 per seat-km. Is there any evidence to suggest that the mean carbon emission for the 747-8 is lower than that of the A380? Justify your answer.