Answer:
7.44√
Step-by-step explanation:
find the average of his scores:
98 +78+84 +75 +91 = 426/5 = 85.2
now find the difference between the average and each test score:
98 - 85.2 = 12.8
85.2 -78 = 7.2
85.2 - 84 = 1.2
85.2 -75 = 10.2
91-85.2 = 5.8
total those and divide by the number of tests
12.8 + 7.2 + 1.2 +10.2 +5.8 =37.2/5 = 7.44
