Biology and environment science motor vehicles contribute

Question

Question: Biology and Environment Science Motor vehicles contribute approximately 15% of all carbon dioxide released into the atmosphere each year. Carbon dioxide emissions are often used to determine if a motor vehicle is efficient, or green. A random sample of 40 2013 automobiles was obtained and the CO₂ emissions for each was measured (in g/mi). The mean CO₂ emissions for all automobiles tested by the U.S. Environmental Protection Agency in 2012 was 335 g/mi. Is there any evidence that the mean CO₂ emissions has decreased? Assume σ = 65 and use a = 0.05. Write a Solution Trail for this problem.