5.0.1949,0.0031

6.0.157, 0.301

7.42.8, 45.6

8.3840, 4134

5. A recent study of the lifetimes of cell phones found the average is 24.3 months. The standard deviation is 2.6 months (6 points each). a. If a random sample of 20 cell phones is selected, find the probability that the sample mean lifetime will be less than 23.8 months. b. If a random sample of 30 cell phones is selected, find the probability that the sample mean lifetime is more than 25.6 months. The answer to part a) is and the answer to part b) is Please round final answers to 4 decimal places.6. The drug OxyContin is used to treat pain, but it is dangerous because it is addictive and can be lethal. In clinical trials, 227 subjects were treated with OxyContin and 52 of them developed nausea. Construct the 99% confidence interval of the true proportion of OxyContin users who develop nausea. Please round final answer to 3 decimal places. (8 points) The lower bound of the confidence interval is and the upper bound of the confidence interval is Please round final answers to 3 decimal places.7. A random sample of 15 registered nurses in a large hospital showed that they worked on average 44.2 hours per week. The standard deviation of the sample was 2.6. Find the 95% confidence interval of the true mean. (8 points) The lower bound of the confidence interval is hours/week and the upper bound of the confidence interval is hours/week. Please round final answers to 1 decimal place.8. A random sample of 50 four-year-olds attending day care centers provided a yearly tuition mean rate of $3987 with a population standard deviation of $630. Find the 90% confidence interval of the true mean annual day care cost. Round final answer to the nearest dollar. (8 points) The lower bound of the confidence interval is $ and the upper bound of the confidence interval is $ Please round to nearest whole number