In: Statistics and Probability
For problems 1 and 2, the list shows the results of a study on the use of plus/minus grading at North Carolina State University. It shows the percents of graduate and undergraduate students who received grades with pluses and minuses (for example, C+, A-, etc.)
-Of all students who received one or more plus grades, 92% were undergraduates and 8%
were graduates
- -Of all students who received one or more minus grades, 93% were undergraduates and
7% were graduates
Find the probability that a student is an undergraduate student, given that the student received a plus grade.
Find the probability that a student is a graduate student, given that the student received a minus grade.
Undergraduate | Graduate | |
Plus grade | 92% | 8% |
Minus grade | 93% | 7% |
Let , A be the event that the student is an undergraduate student and B be the event that the student received a plus grade.
Let , be the event that the student is an undergraduate student and the student received a plus grade.
Now , P(A)=0.92 , P(B)=0.92+0.08=1.00 , = 0.92
Now , By using the definition of conditional probability,
Therefore , the probability that a student is an undergraduate student, given that the student received a plus grade is 0.92
2 )
Let , A be the event that the student is graduate student and B be the event that the student received a minus grade.
Let , be the event that the student is graduate student and the student received a minus grade.
Now , P(A)=0.0.07 , P(B)=0.93+0.07=1.00 , = 0.07
Now , By using the definition of conditional probability,
Therefore , the probability that a student is graduate student, given that the student received a minus grade is 0.07