The Centers for Disease Control (CDC) determined that the average life expectancy for the U.S. population in 2018 was 78.7 years. After learning this you decide to collect data from a random sample of New York City obituaries from 2018-2020 to compare the life expectancy of New York City residents to all United States citizens. After surveying 42 obituaries, you find a mean life expectancy of 81.9 years with a sample standard deviation of 8.3 years.

(a) Use the 2SD Method (statistic 2 * standard error) to calculate (by hand) a 95% confidence interval for each parameter. Round your proportions to 4 decimals.

(b) Interpret the confidence intervals using the units and terminology from the scenario.

(c) Use the confidence interval to determine whether the average life expectancy of New York City residents is the same as the national average life expectancy.