Scores on a certain test are normally distributed with a variance of 91. A researcher wishes to estimate the mean score achieved by all adults on the...

Scores on a certain test are normally distributed with a variance of 91. A researcher wishes to estimate the mean score achieved by all adults on the test. Find the sample size needed to assure with 95.44 percent confidence that the sample mean will not differ from the population mean by more than 2 units.