A study directed at measuring the fatigue and stress on air traffic controllers has resulted in a recommendation to redesign the controllers' work stations. Three specific alternatives have been selected as having the best potential for reducing controller stress. To test these alternatives, the three types of work stations were installed in an air traffic control center, and six controllers were selected at random and assigned to operate each of the systems. Medical exams were used to determine controller stress levels after operating each system. The results are summarized in the table below (low numbers = low stress)

System A System B System C

Controller 1 15 15 18
Controller 2 14 14 14
Controller 3 10 11 15
Controller 4 13 12 17
Controller 5 16 13 16
Controller 6 13 13 13