ex. A soft drink company produces 20 oz. bottles of ice tea. To check whether its filling process is running correctly it randomly samples 80 bottles from the assembly line after they are filled and the volume of the contents is measure. The volume of ice tea in the bottles is assumed to have a standard deviation of 0.5. If the average volume of a sample of 80 bottles is 19.86 oz. is the machine correctly filling the bottles to the mean volume at level α = 0.05.