A nurse at a local hospital is interested in estimating the birth weight of infants. How large a sample must she select if she desires to be 90?% confident that the true mean is within 2 ounces of the...

A nurse at a local hospital is interested in estimating the birth weight of infants. How large a sample must she select if she desires to be 90?% confident that the true mean is within 2 ounces of the sample? mean? The population standard deviation of the birth weights is known to be 8 ounces.