A machine that stuffs a cheese-filled snack product can be adjusted for the amount of cheese injected into each unit

A machine that stuffs a cheese-filled snack product can be adjusted for the amount of cheese injected into each unit. A simple random sample of 30 units is selected, and the average amount of cheese injected is found to be x = 3.5 grams. If the process standard deviation is known to be ? = 0.25 grams, construct the 95% confidence interval for µ = the average amount of cheese being injected by the machine.

Solution: By definition, the 95% confidence interval for the population mean is given by