An econometrics class has 80 students, and the mean student weight is 145 lb. a random sample of four students is selected from the class, and their average weight is calculated. will the average weight of the students in the sample equal 145lb?

The total weight of 80 students is 80 * 145 = 11600 lb

If a sample of four students taken, their total weight divided by 4 would not necessarily give 145lb. The weight of each of the four students could be from the lightest end of the range or could be from the heaviest end of the range.