Answer Happy

1. A sample of 14 randomly selected commuters in Chicago showed the average of the commuting times was 33.2 minutes. If the standard deviation was 8.3 minutes, find the 95% confidence interval of the true mean. (30 pts) 2. A large furniture store has begun a new ad campaign on local television. Before the campaign, the long term mean daily sales were $24,819. A random sample of 40 days during the new ad campaign gave a sample mean daily sale of x = $25, 910. Does this indicate that the population mean daily sales is now more than $ 24,819? Use a 1% level of significance. Assume o = $1917. (35 pts) 3. In the 1999 National Health Interview Survey (A-6), researchers found that among U.S. adults75 or older, 34 percent had lost all their natural teeth and for U.S. adults ages 65-74, 26 percent had lost all their natural teeth. Assume that these proportions are the parameters for the United States in those age groups. If a random sample of 200 adults ages 65-74 and an independent random sample of 250 adults ages 75 or older are drawn from these populations, find the probability that the difference in percent of total natural teeth loss is less than 5 percent between the two populations.