The estimate of the population parameter is 5 feet and 5 inches, or D. Assuming the survey was a random sample of the 3,500 students, we can reasonable infer that the the chosen 350 students is a accurate representation of the entire student body. Since the mean, or average, height of the surveyed students was 5 feet and 5 inches, we can further infer that this height is also an accurate representation of the student body. Therefore showing that D is correct.
