An urban economist wishes to estimate the mean amount of time people spend travelling to work. He obtains a random sample of 60
individuals who are in the labour force and finds that the mean travel time is 30.5 minutes. Assuming that the population standard deviation of travel time is 20.5 minutes, construct and interpret a 90% confidence interval for the mean travel time to work. (Note: the standard deviation is large, because some people work at home and thus travel 0 minutes and some people take transit which results in large travel times).
An urban economist wishes to estimate the mean amount of time people spend traveling to work. He obtains a random sample of 50 individuals who are in the labor force and finds that the mean travel time is 24.2 minutes. Assuming the population standard deviation of travel time is 18.5 minutes, construct and interpret a 95% confidence interval for the mean travel time to work. Note: The standard deviation is large because many people work at home (travel time =0 minutes) and many have commutes in excess of 1 hour. (Source: Based on data obtained from the American Community Survey.)
Explanation:
An urban economist wishes to estimate the mean amount of time people spend traveling to work. He obtains a random sample of 50 individuals who are in the labor force and finds that the mean travel time is 24.2 minutes. Assuming the population standard deviation of travel time is 18.5 minutes, construct and interpret a 95% confidence interval for the mean travel time to work. Note: The standard deviation is large because many people work at home (travel time =0 minutes) and many have commutes in excess of 1 hour. (Source: Based on data obtained from the American Community Survey.)
