The Psychopathy Checklist – Revised (PCL—R) is an assessment tool used to identify psychopaths, with scores ranging from 0 to 40 (a score of 30 or higher being indicative of psychopathy). A forensic psychologist interested in the prevalence of psychopaths in a prison administered the PCL—R to 74 random prison inmates and obtained the following distribution of scores. Convert this into a grouped frequency distribution containing five class intervals, and
(a) Determine the size of the class intervals,
(b) Indicate the upper and lower limits of each class interval,
(c) Identify the midpoint of each class interval,
(d) Find the percentage for each class interval,
(e) Find the cumulative frequency for each class interval, and
(f) Find the cumulative percentage for each class interval.
N = 74