Solve the problem. A certain HMO is attempting to show the benefits of managed ca re to an insurance company. The HMO believes that certain types of doctors are more cost-effective than others. One theory is that certication level is an important factor in measuring the cost-effectiveness of physicians. To investigate this, the HMO obtained independent random samples of 17 physicians from each of the three certification levelsBoard certified {C}; Uncertified, board eligible {E}; and Uncertified, board ineligible [l] and recorded the total per member per month charges for each (a total of 51 physicians]. How many factors are present in this study? OA} 1