Platelet monoamine oxidase (MAO) is an index of brain serotonin ac- tivity. Low MAO levels have been found to be related to behaviour disorders. In a particular study, the MAO activity levels of 30 patients with bulimia nervosa were measured. The average level of MAO activ- ity for the 30 bulimic patients was 4.35 nmol/108 platelets/hour, with a standard deviation of 2.75 nmol/108 platelets/hour.
(a) Based on this data, give a 95% confidence interval for the average MAO activity level of bulimic patients. Assume that the level of MAO activity is normally distributed.
(b) The normal range for the MAO levels is between 5.5 and 8.5. How does the interval constructed in part 3a compare with the normal range? What conclusions can be drawn?