Name: ______Date: ______
Statistics Sections 7-2 through 7-4 Quest
Directions: Complete all of the following questions. If you use a formula, make sure you write the formula, then plug in the values.
(1)What is the critical value that corresponds to a
- 90% confidence level?______
- 95% confidence level?______
- 99% confidence level?______
(2)What is the critical value that corresponds to a
- Sample size of 15 and a confidence level of 95%?______
- Sample size of 185 and a confidence level of 99%?______
- Sample size of 76 and a confidence level of 90%?______
(3)An important issue facing Americans is the large number of medical malpractice lawsuits and the expenses that they generate. In a study of 1228 randomly selected medical malpractice lawsuits, it is found that 856 of them were later dropped or dismissed (based on data from the Physician Insurers Association of America.) Construct a 99% confidence interval estimate of the proportions of medical malpractice lawsuits that are dropped or dismissed. Does it appear that the majority of such suits are dropped or dismissed?
(4)A study of the ages of motorcyclists killed in crashes involved the random selection of 150 drivers with a mean of 37.1 years (based on data from the Insurance Institute for Highway Safety). Assuming that =12.0 years, construct a 99% confidence interval estimate of the mean age of all motorcyclists killed in crashes. If the confidence interval limits do no include ages below 20 years, does it mean that motorcyclists under the age of 20 rarely die in crashes?
(5)Many states are carefully considering steps that would help them collect sales taxes on items purchased on the Internet. How many randomly selected sales transactions must be surveyed to determine the percentage that transpired over the Internet? Assume that we want to be 99% confident that the sample percentage is within two percentage points of the true population percentage of all sales transactions.
(6)Nielson Media Research wants to estimate the mean amount of time (in minutes) that full-time college students spend watching television each weekday. Find the sample size necessary to estimate that mean with a15-min margin of error. Assume that a 95% confidence level is desired. Also assume that a pilot study showed that the standard deviation is estimated to be 112.2 min.
(7)If the difference in temperature for each day in a random sample is found, the result is a list of 35 values with a mean of -1.3˚ and a standard deviation of 4.7˚. Construct a 95% confidence interval estimate of the mean daily difference in temperature. Does the confidence interval include 0˚? If a meteorologist claims that temperatures tend to change by 1.5˚ a day, does this claim appear to be valid? Why or why not?