The schiffert health center at virginia tech wants to see if putting antibacterial soap in the dormitory bathrooms will reduce the number of visits to the infirmary. vt has 47 on-campus residence halls. they are home for 9300 students. twenty residence halls have been randomly selected. in all 2,000 students spanning over the selected halls. half of the selected dormitories are chosen at random and supplied with the special soap; the remaining ones were supplied with regular soap. at the end of the semester, the two types of soap are compared using the number of visits to the infirmary per person per semester. a) why is this example of an experimental study and not an example of an observational study? b) are the observational units and the experimental units the same? c) name at least two blocking factors that could exist in this experimental study. d) name at least three variables that would appear in the sample dataset. e) name at least one confounding variable that can exist to debate the validity of the findings.