Question

22

A researcher is interested in finding a 98% confidence interval for the mean number minutes students are concentrating on their professor during a one hour statistics lecture. The study included 101 students who averaged 35.2 minutes concentrating on their professor during the hour lecture. The standard deviation was 12.1 minutes. Round answers to 3 decimal places where possible.

a. To compute the confidence interval use a

distribution.

b. With 98% confidence the population mean minutes of concentration is between and minutes.

c. If many groups of 101 randomly selected members are studied, then a different confidence interval would be produced from each group. About percent of these confidence intervals will contain the true population mean minutes of concentration and about percent will not contain the true population mean minutes of concentration.

23

You want to obtain a sample to estimate a population mean. Based on previous evidence, you believe the population standard deviation is approximately σ=49.2. You would like to be 99% confident that your estimate is within 2.5 of the true population mean. How large of a sample size is required?

n =

24

A newsgroup is interested in constructing a 99% confidence interval for the proportion of all Americans who are in favor of a new Green initiative. Of the 600 randomly selected Americans surveyed, 401 were in favor of the initiative. Round answers to 4 decimal places where possible.

a. With 99% confidence the proportion of all Americans who favor the new Green initiative is between and .

b. If many groups of 600 randomly selected Americans were surveyed, then a different confidence interval would be produced from each group. About percent of these confidence intervals will contain the true population proportion of Americans who favor the Green initiative and about percent will not contain the true population proportion.

Answer 1