Suppose that in the population of children in the United States, the average number of minutes per day spent exercising is 30 with a standard deviation of 7. I select a random sample of 12 children and find that they spend an average of 40 minutes exercising with a standard deviation of 10. Please use this information to answer the following questions.

d. Compare the two standard errors that you calculated in Questions b (using z score) and c (using t value). Why are they different?