A psychologist makes use of a test instrument for measuring depression. The instrument is known to have a mean score of 70 for normal individuals. Twenty individuals who have been described as severely depressed by a therapist takes the tests. A psychologist is interested to know if the average test score made by severely depressed individuals is greater than 70. The data are reflected on the table below. Scores Made by Severely Depressed Individuals No. Score No. Score ERSIT 75 11 75 2 77 12 74 3 73 13 63 80 14 76 65 15 67 74 16 70 75 17 69 8 69 18 76 71 19 65 10 72 20 68