A confidence interval can be constructed using formula 17.1, where a value of z from the standard normal table is multiplied by the standard error (S....

      A confidence interval can be constructed using formula 17.1, where a value of z from the standard normal table is multiplied by the standard error (S.E.) and this value is both added to and subtracted from the mean. In order to use this formula, the (11) ---------

 must be known and sample size must be at least (12)---------