a section of a plant packages of mized nuts are filled and sealed in a series of mechanical steps.

"a section of a plant packages of mized nuts are filled and sealed in a series of mechanical steps. The weights of the population of finished packages are normally distributed with a mean of 75 grams and a standard deviation of 4 grams. Quality control personnel sample nine bags each hour and recond the mean weight of each sample. Calculate the mean and the standard deviation of these sample means