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...

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).19 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 s 5 65 and use a 5 0.05. Write a Solution Trail for this problem.

After analyzing a database of over 2 million telephone calls, Vonage reported that the mean length of all international calls was 295 seconds. Following an extensive advertising campaign, the company expected the length of international calls to increase. A few months after the ads first appeared, a random sample of 48 calls was obtained. The sample mean was x = 306.3 seconds. Assume that the population standard deviation is 52 seconds. Is there any evidence to suggest the advertising campaign has been successful? Use a = 0.01.