A) We simply look for the grade with the largest frequency, which would be
4 since it was obtained 12 times.
B) Because this sample has 50 observations, our median will be the average of the 25th and 26th largest. To see this, let's add in a third column to that table  cumulative frequency.
FREQUENCY CUM. FREQ. GRADE
4 4 1
8 12 2
7 19 3
12 31 4
4 35 5
9 44 6
3 47 7
1 48 8
2 49 9
We can see that the 25th and 26th observations are both 4 since both 25 and 26 fall between 31 and 17 (the cumulative frequencies of 4 and 3, respectively.) So our median is
4.
C) First of all, we find the sum of the grades obtained. This is just a matter of multiplying the grade by its frequency and adding those results together:
(1 * 4) + (2 * 8) + (3 * 7) + (4 * 12) + (5 * 4) + (6 * 9) + (7 * 3) + (8 * 1) + (9 * 2) =
210
We then find the average score in order to find our mean. That means our mean is 210/50 =
4.2.
11/13/2013

Carlo S.