To find out whose mean test score will increase the most, we need to calculate the mean of each student's previous six test scores and compare it to their current score of 100.
Theo: 84, 88, 81, 85, 77, 76
Mean: (84 + 88 + 81 + 85 + 77 + 76) / 6 = 81.83
Increase: 100 - 81.83 = 18.17
Jose: 91, 93, 97, 96, 96, 96
Mean: (91 + 93 + 97 + 96 + 96 + 96) / 6 = 95.83
Increase: 100 - 95.83 = 4.17
Dana: 68, 74, 83, 80, 81, 82
Mean: (68 + 74 + 83 + 80 + 81 + 82) / 6 = 77.67
Increase: 100 - 77.67 = 22.33
Ara: 100, 98, 99, 97, 100, 100
Mean: (100 + 98 + 99 + 97 + 100 + 100) / 6 = 99
Increase: 100 - 99 = 1
Therefore, Dana's mean test score will increase the most at 22.33.