We are given a table showing the frequency of responses for a test grade.
Test Grade
Frequency
A
7
B
11
C
6
D
3
F
1
A probability distribution shows the probability of each possible outcome. To find the probability distribution for the test grades, we will start by finding the total number of responses. To do so we will add the frequencies.
7+ 11+ 6+ 3+ 1= 28
Finally, we will write each frequency as a fraction of the total number of responses. This will give us the probability of each grade.
Test Grade
Frequency
Probability
A
7
7/28=1/4
B
11
11/28
C
6
6/28
D
3
3/28
F
1
1/28
We can now use our table to find the desired probability.
P(B or C)=P(B)+P(C) ⇕
P(B or C)=11/28+6/28=17/28
