To measure the effectiveness of treatment, researchers often measure individuals before and after treatment, and record the amount of difference between the two scores. If the differences average around zero, it is an indication that the treatment has no effect. However, if the differences are consistently positive (or consistently negative), it suggests that the treatment does not have an effect. Hypothetical data, similar to the results of the study, are as follows. Note that each score measures the difference in pain level after treatment compared to the pain level before treatment.
Note: A positive score indicates more pain before treatment than after treatment.
+4, +5, +2, 0, +7, +4, +3, +3, +2, -2, +1, +6, 0, +4, +7, -1, +3, +5, +4, +2
A. Sketch a histogram showing the frequency distribution for the different scores.