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A market researcher plans to sample sales receipts at a natural food store to estimate the average size (in dollars) of a customer purchase. Previous analysis suggests that the standard deviation of the purchase amount is approximately $25.
In order to calculate a 95% confidence interval of total width less than $5, how many sales records should the researcher include in her sample?
E) 97.
F) 271.
G) 385.
H) The answer can not be determined from the information provided.