In: Statistics and Probability
A university conducted a survey of
273
sophomore, junior, and senior undergraduate students regarding satisfaction with student government. Results of the survey are shown in the table by class rank.
Sophomore |
Junior |
Senior |
Total |
||
Satisfied |
45 |
65
63
173
Neutral |
16 |
16
9
41
Not satisfied |
17 |
15
27
59
Total |
78 |
96
99
273
A survey participant is selected at random. What is the probability that he or she is a
junior
AND
neutral
?
In other words, find P(person is a
junior
AND
neutral
Let A be the event that the selected participant is junior.
Let B be the event that the selected participant is neutral.
Now to find the probability that the selected participant is junior and neutral , we make use of the conditional probability given by,
To find the probability that the selected person is junior given he is neutral (i.e) P(A|B):
Number of selected participants who are neutral(B) is 41 and the number of juniors(A) among the neutral participants is 16.
Thus the probability that the selected person is junior given he is neutral = 16/41 =0.39
To find the probability that the selected person is neutral (i.e) P(B):
Number of selected participants who are neutral(B) is 41.
Total number of selected participants is 273.
Thus the probability of selected participant is neutral =41/273=0.15
TO FIND THE PROBABILITY THAT THE PERSON IS JUNIOR AND NEUTRAL:
Since
Thus the P[person is junior and neutral] is 0.059.