# Question

The U.S. Energy Information Administration (US EIA) reported that the average price for a gallon of regular gasoline is \$3.94 (US EIA website, April 6, 2012). The US EIA updates its estimates of average gas prices on a weekly basis. Assume the standard deviation is \$.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.
a. The desired margin of error is \$.10.
b. The desired margin of error is \$.07.
c. The desired margin of error is \$.05.

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