A manufacturer of healthcare products claims that the mean amount of lotion in its 18 fl. oz bottles is 535 mL. To investigate whether this claim is too low a random sample of 10 bottles was taken and the actual amount of contents measured. The sample produced a mean of 535 mL with a standard deviation of 0.47 mL. Assume that the distribution of the amount of lotion is approximately normal.
What is the appropriate test statistic for this hypothesis test?