A psychologist wants to test the effectiveness of a therapy for depression and collects the data from 12 patients on Beck Depression Inventory (BDI). BDI consists of 21 depression symptoms (e.g., sadness, dislike of self) and asks to what extent each symptom applies to the individual under investigation (score ranging from 1 to 3). The maximum score of BDI is 63 and the score is interpreted as follows: Possible denial, faking that all is well; this is a score not usually given by healthy people 5 -9 Ups and downs within the normal range 10 - 18 Mild to moderate depression 19 -29 Moderate to severe depression 30 -63 Severe depression Before the therapy starts, the psychologist asks a relative of each patient to complete the BDI for that patient. Then the patient takes part in the therapy which lasts for 12 weeks. Six months after the therapy the psychologist asks the same relatives to complete the BDI once more. Patient ID BDI (Before Therapy) BDI (After Therapy) 36 24 2 27 18 45 30 25 8 34 27 6 28 14 51 47 30 31 9 33 5 10 47 27 11 32 16 12 26 23