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# Normal Distribution

The Oil Price Information Center reports the mean price per gallon of regular gasoline is \$3.26 with a population standard deviation of \$0.18. Assume a random sample of 40 gasoline stations is selected and their mean cost for regular gasoline is computed.

a. What is the standard error of the mean in this experiment?
b. What is the probability that the sample mean is between \$3.24 and \$3.28?
c. What is the probability that the difference between the sample mean and the population mean is less than 0.01?
d. What is the likelihood the sample mean is greater than \$3.34?

#### Solution Preview

The Oil Price Information Center reports the mean price per gallon of regular gasoline is \$3.26 with a population standard deviation of \$0.18. Assume a random sample of 40 gasoline stations is selected and their mean cost for regular gasoline is computed.

a. What is the standard error of the mean in this experiment?

Standard deviation =s= \$0.18
sample size=n= 40
sx=standard error of mean=s/square root of n= \$0.0285 = ( 0.18 /square root of 40)