1. Inspection of a random sample of 25 aircraft showed that 17 needed repairs to fix a wiring problem that might compromise safety.

How large a sample would be needed to estimate the true proportion of jets with the wiring problem, with 90 percent confidence and an error of 5 percent? (Enter your answer as a whole number (no decimals). Use a z-value taken to three decimal places in your calculations.)

Sample size = ?

2. How large a sample size would be needed to estimate the percentage of wireless routers in San Francisco that use data encryption, with an error of 2 percent and 95 percent confidence? (Enter your answer as a whole number (no decimals)

Sample size = ?

3. What sample size would be required to estimate the true proportion of American female business executives who prefer the title "Ms.," with an error of 0.025 and 98 percent confidence? (Enter your answer as a whole number (no decimals). Use a z-value taken to three decimal places in your calculations.)

Sample size = ?

4. Analysis showed that the mean arrival rate for vehicles at a certain Shell station on Friday afternoon last year was 4.5 vehicles per minute. How large a sample would be needed to estimate this year's mean arrival rate with 98 percent confidence and an error of 0.5? (Round the standard deviation answer to 4 decimal places. Enter your answer as a whole number (no decimals). Use a z-value taken to four decimal places in your calculations.)

Sample size = ?

5. The EPA city/hwy mpg range for a Saturn Vue FWD automatic 5-speed transmission is 20 to 28 mpg.

(a) Estimate using Assume Normal Population Method. (Round your answer to 4 decimal places.)

Estimate = ?

(b) If you owned this vehicle, how large a sample (e.g., how many tanks of gas) would be required to estimate your mean mpg with an error of 1 mpg and 90 percent confidence? (Enter your answer as a whole number (no decimals). Use a z-value taken to three decimal places in your calculations.)

Sample size = ?

6. The fuel economy of a 2011 Lexus RX 350 2WD 6 cylinder 3.5 L automatic 5speed using premium fuel is a normally distributed random variable with a mean of = 25.75 MPG and a standard deviation of = 2.75 MPG.

(a) What is the standard error of X, the mean from a random sample of 36 fillups by one driver? (Round your answer to 4 decimal places.)

Standard error of X = ?

(b) Within what interval would you expect the sample mean to fall, with 99 percent probability? (Round your answers to 4 decimal places.)

The interval is from ? TO ?

7. The Ball Corporation's beverage can manufacturing plant in Fort Atkinson, Wisconsin, uses a metal supplier that provides metal with a known thickness standard deviation = 0.000631 mm. If a random sample of 46 sheets of metal resulted in an X = 0.3293 mm.

Calculate the 90 percent confidence interval for the true mean metal thickness. (Round your answers to 4 decimal places.)

The 90% confidence interval ? to ?

8. The Ball Corporation's beverage can manufacturing plant in Fort Atkinson, Wisconsin, uses a metal supplier that provides metal with a known thickness standard deviation = 0.00097 mm. If a random sample of 48 sheets of metal resulted in an X = 0.1646 mm.

Calculate the 95 percent confidence interval for the true mean metal thickness. (Round your answers to 4 decimal places.)

The 95% confidence interval ? to ?

9. The fuel economy of a 2011 Lexus RX 350 2WD 6 cylinder 3.5 L automatic 5-speed using premium fuel is a normally distributed random variable with a mean of = 25.0 MPG and a standard deviation of = 1.25 MPG.

What is the standard error of X, the mean from a random sample of 16 fill-ups by one driver? (Round your answers to 4 decimal places.)Within what interval would you expect the sample mean to fall, with 90 percent probability? (Round your answers to 4 decimal places.)

The interval is from ? to ?