1.)

The U.S. Energy Information Administration (US EIA) reported that the average price for a gallon of regular gasoline is $2.94. The US EIA updates its estimates of average gas prices on a weekly basis. Assume the standard deviation is $0.25 for the price of a gallon of regular gasoline and recommend the appropriate sample size for the US EIA to use if they wish to report each of the following margins of error at 95% confidence. (Round your answers up to the nearest whole number.)

(a)

The desired margin of error is $0.10.

(b)

The desired margin of error is $0.06.

(c)

The desired margin of error is $0.04.

2.)

Customers arrive at a movie theater at the advertised movie time only to find that they have to sit through several previews and prepreview ads before the movie starts. Many complain that the time devoted to previews is too long. A preliminary sample conducted by The Wall Street Journal showed that the standard deviation of the amount of time devoted to previews was 6 minutes. Use that as a planning value for the standard deviation in answering the following questions. (Round your answers up to the nearest whole number.)

(a)

If we want to estimate the population mean time for previews at movie theaters with a margin of error of 105 seconds, what sample size should be used? Assume 95% confidence.

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(b)

If we want to estimate the population mean time for previews at movie theaters with a margin of error of 1 minute, what sample size should be used? Assume 95% confidence.

____________________

3.)

A simple random sample of 400 individuals provides 152 Yes responses.

a)

What is your estimate of the standard error of the proportion, _p?

(Round your answer to four decimal places.)

___________________________

b)

Compute the 95% confidence interval for the population proportion. (Round your answers to four decimal places.)

___________________ to _______________________

4.)

At 95% confidence, how large a sample should be taken to obtain a margin of error of 0.08 for the estimation of a population proportion? Assume that past data are not available for developing a planning value for p*.

(Round your answer up to the nearest whole number.)

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