a cereal company produces boxes of choco-sugar balls, the weights of these boxes is normally distributed with a known standard deviation of o=0.5 oz. A sample of 64 boxes is taken and the mean weigth of the sample is found to be x=16.4oz. What is the z a/2 for a confidence level of 95%, the margin error of this sample and give a 95% confidence interval for the mean weight of boxes produced based on the sample mean of 16.4?