1.

The mean and standard deviation of a random sample of n measurements are respectively equal to 33.9 and 3.3.

a) Find a 95% confidence interval for if n = 100

b) Find a 95% confidence interval for if n = 400

c) Find the widths of the confidence intervals you calculated in parts a and b. What is the effect on the width of a confidence interval of quadrupling the sample size while holding the confidence level constant?

2.

Listed below are the ages (in years) of randomly selected race car drivers. Construct a 95% confidence interval estimate of the mean age of all race car drivers.

32 32 33 33 41 29 38 32 33 23 27 45 52 29 25

3.

According to Bride's Magazine, the cost of a wedding these days can be expensive when the costs of the reception, engagement ring, bridal gown, and pictures, etc., are included. Shao Wei wants to estimate the mean cost for a wedding. From a random sample of 115 recent U.S. weddings, the mean cost was $18,945 and the standard deviation was $8,280.

a) Construct a 90% confidence interval for the population mean cost for a wedding.

b) Determine the minimum required sample size to construct a 90% confidence interval so that the sample mean is within $1,000 of the population mean.

4.

Listed below are the numbers of years it took for a random number of college students to earn bachelor's degree (based on a research study). Construct a 99% confidence interval estimate of the mean time required for all college students to earn bachelor's degrees. Does the confidence Interval contain a value of 4 years? What conclusion can you draw from your answer?

4 4 4 4 4 4 4.5 4.5 4.5 4.5 4.5 4.5 6 6 8 9 9 13 13 15

5.

In a survey of 3005 adults aged 57 through 85 years, it was found that 81.7% of them used at least one prescription medication.

a) Construct a 90% confidence interval estimate of percentage of adults aged 57 through 85 years who used at least one prescription medication

b) What do the results tell us about college students who used at least one prescription medication?