A human resources (HR) manager wants to see if she can predict job success from a college graduate's final average grade. The manager collects data for a random sample of employees hired in the last two years. The employees ‘grades are in the personnel files (all are college graduates). The HR manager also asks each employee's supervisor to score the employee's performance, using a detailed questionnaire to arrive at a score from 0 (meaning the worst possible performance) to 100 (an outstanding performance). What kind of data are these? Do you see any difficulty with drawing conclusions based on such a study?