A behavior therapist is about to begin working with an ADHD (attention-deficit/ hyperactivity disorder) child in a classroom setting to reduce the number of times he gets out of his seat, talks out of turn, or goes off-task. To establish a baseline, the therapist observes the child for an hour each morning and afternoon for 5 days, keeping a tally of the target behaviors. Here are the therapist’s behavior tallies for the 10 observation periods.

Find the 

(a) Range, 

(b) Variance, and 

(c) Standard deviation of the statistics test scores. Show your work.

4 8 7 5 12 9 8 5 7 4