A researcher is interested in whether high school students who play sports have a higher or lower body mass index (BMI) than students in the general population. The researcher is unsure of whether playing sports will decrease body mass or increase body mass. The researcher selects a sample of 60 athletes and finds that there average BMI is 22. The average in the general population of students is 22.5 with a standard deviation of 3. what is the zobt for this sample.