Lucia has been recording her grades on her Spanish quizzes. The following is a list of her grades:

74, 81, 86, 92, 74, 85, 90, 89, 78, 80

Determine the mean absolute deviation of Lucia’s Spanish quiz grades.

5.5

82.9

8.29

55

1 answer

To find the mean absolute deviation of Lucia's Spanish quiz grades, first find the mean of the grades:

(74 + 81 + 86 + 92 + 74 + 85 + 90 + 89 + 78 + 80) / 10 = 829 / 10 = 82.9

Next, find the absolute deviation for each grade by subtracting the mean from each individual grade:

|74 - 82.9| = 8.9
|81 - 82.9| = 1.9
|86 - 82.9| = 3.1
|92 - 82.9| = 9.1
|74 - 82.9| = 8.9
|85 - 82.9| = 2.1
|90 - 82.9| = 7.1
|89 - 82.9| = 6.1
|78 - 82.9| = 4.9
|80 - 82.9| = 2.9

Add up all the absolute deviation values:

8.9 + 1.9 + 3.1 + 9.1 + 8.9 + 2.1 + 7.1 + 6.1 + 4.9 + 2.9 = 55

Find the average of the absolute deviation values:

55 / 10 = 5.5

Therefore, the mean absolute deviation of Lucia's Spanish quiz grades is 5.5.