Question 1
A survey of 76 commercial airline flights of under 2 hours resulted in a sample average late time for a flight of 2.37 minutes. The population standard deviation was 12 minutes. Construct a 95% confidence interval for the average time that a commercial flight of under 2 hours is late. What is the point estimate? What does the interval tell about whether the average flight is late?

*Round your answers to 2 decimal places, the tolerance is +/-0.01.

* ≤ μ ≤ *

The point estimate is .

The interval is . Since zero is in the interval, there is a possibility that, on average, the flights are .

Question 2
What is the average length of a company's policy book? Suppose policy books are sampled from 45 medium-sized companies. The average number of pages in the sample books is 213, and the population standard deviation of 48. Use this information to construct a 98% confidence interval to estimate the mean number of pages for the population of medium-sized company policy books.

Round your answers to 2 decimal places, the tolerance is +/-0.01.

≤ µ ≤

Question 3
A random sample of size 20 is taken, resulting in a sample mean of 15.40 and a sample standard deviation of 2.56. Assume x is normally distributed and use this information and α = .05 to test the following hypotheses.

Round your answer to 2 decimal places, the tolerance is +/-0.01.

Question 15
According to the U.S. Bureau of Labor Statistics, the average weekly earnings of a production worker in 1997 were $424.20. Suppose a labor researcher wants to test to determine whether this figure is still accurate today. The researcher randomly selects 55 production workers from across the United States and obtains a representative earnings statement for one week from each. The resulting sample average is $430.75. Assuming a population standard deviation of $33.90, and a 10% level of significance, determine whether the mean weekly earnings of a production worker have changed.

Round your answer to 2 decimal places, the tolerance is +/-0.01.

The value of the test statistic is and we .

Question 33
According to a survey by Runzheimer International, the average cost of a fast-food meal (quarter-pound cheeseburger, large fries, medium soft drink, excluding taxes) in Seattle is $4.82. Suppose this figure was based on a sample of 27 different establishments and the standard deviation was $0.37. Construct a 95% confidence interval for the population mean cost for all fast-food meals in Seattle. Assume the costs of a fast-food meal in Seattle are normally distributed. Using the interval as a guide, is it likely that the population mean is really $4.50? Why or why not?

Round the answers to 4 decimal places.

≤ μ ≤

Since 4.50 in the interval, we are 95% confident that μ 4.50.

Question 35
A national beauty salon chain wants to estimate the number of times per year a woman has her hair done at a beauty salon if she uses one at least once a year. The chain's researcher estimates that, of those women who use a beauty salon at least once a year, the standard deviation of number of times of usage is approximately 6. The national chain wants the estimate to be within one time of the actual mean value. How large a sample should the researcher take to obtain a 98% confidence level?

Round your answer up to the nearest integer.

Sample .

The tolerance is +/- 1.