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Sagot :
Answer:
A 11.1%
Step-by-step explanation:
The students are chosen from a sample without replacement, which means that the hypergeometric distribution is used to solve this question.
Hypergeometric distribution:
The probability of x sucesses is given by the following formula:
[tex]P(X = x) = h(x,N,n,k) = \frac{C_{k,x}*C_{N-k,n-x}}{C_{N,n}}[/tex]
In which:
x is the number of sucesses.
N is the size of the population.
n is the size of the sample.
k is the total number of desired outcomes.
Combinations formula:
[tex]C_{n,x}[/tex] is the number of different combinations of x objects from a set of n elements, given by the following formula.
[tex]C_{n,x} = \frac{n!}{x!(n-x)!}[/tex]
In this question, we have that:
13 + 7 = 20 teachers, which means that N = 20.
7 history teachers means that k = 7.
Two teachers for each student, which means that n = 2.
What is the approximate probability that a random student on the trip will be assigned to a group led by two history teachers?
This is P(X = 2). So
[tex]P(X = x) = h(x,N,n,k) = \frac{C_{k,x}*C_{N-k,n-x}}{C_{N,n}}[/tex]
[tex]P(X = 2) = h(2,20,2,7) = \frac{C_{7,2}*C_{13,0}}{C_{20,0}} = 0.1105[/tex]
So close to 11.1%, and the correct answer is given by option A.
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