Question

using the table

1. What is the probability that a student received a grade A or grade B?

2. what is the probability that student received a grade A, B or C grade?

Assigned Grades for 15 Students

grade	count
A	9
B	2
C	1
D	0
F	3

Answer 1

Solution:

Given:

grade	count
A	9
B	2
C	1
D	0
F	3
	N = 15

Part 1)  What is the probability that a student received a grade A or grade B?

P( a student received a grade A or grade B) = .............?

P( A or B) = .........?

P( A or B) = P(A) + P(B)

P( A or B) = 9/15 + 2/15

P( A or B) =(9+2)/15

P( A or B) =11/15

P( A or B) =0.7333

Part 2) what is the probability that student received a grade A, B or C grade?

P( A , B or C) =...........?

P( A , B or C) = P(A) + P(B) +P(C)

P( A , B or C) = 9/15 + 2/15 +1 /15

P( A , B or C) = ( 9+2+1)/15

P( A , B or C) =12/15

P( A , B or C) =0.8