In a campus survey, we observed the students at the entrance of library in 1 hou
ID: 3022043 • Letter: I
Question
In a campus survey, we observed the students at the entrance of library in 1 hour and recorded the hair style for each of them, as shown in the table. Based on the information in the table, we are interested in making predictions.
(1) What portion of the population is male?
(2) If you are waiting outside the library, what is the probability that the next person coming to the library has long hair?
(3) If you know one person coming to the library has long hair, what is the probability that the person is a male?
(4) If you know one person coming to the library is a male, what is the probability that has long hair?
Female 15 45 90 Male Long Hair Middle Hair Short Hair 50 40 10Explanation / Answer
Consider:
a)
P(M) = 150/250 = 0.6 [ANSWER]
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b)
P(L) = 65/250 = 0.26 [ANSWER]
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c)
P(M|L) = 15/65 = 0.230769231 [ANSWER]
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d)
P(L|M) = 15/150 = 0.1 [ANSWER]
M F Total L 15 50 65 M 45 40 85 S 90 10 100 Total 150 100 250