A lotion company produces lotion bottles that hold 8 ounces of lotion. Periodically, the company gets complaints that their lotion bottles are not holding enough lotion. To test this claim, the lotion company randomly samples 16 lotion bottles and finds the average amount of lotion held by the lotion bottles is 7.7 ounces with a standard deviation of 0.4 ounce. Calculate the appropriate test statistic.