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 $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 a desired margin of error of $0.05 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.