Mathematics Asked by Joseph Bungabong on February 6, 2021
A committee of $m$ students is being formed by randomly selecting from a population of n undergraduate students in an engineering college (note: m < n). Assume that you are also included in this population of students. What is the probability that you will be among the $m$ selected students?
Since you’re choosing $m$ amount of students to be in a committee from a population $n$, then the probability of any student being in the committee is $left(frac{m}n right)$. But the probability of you being chosen is $left(frac{1}m right)$. Since the students being selected are not replaced, I used the following equation:
$$
frac{left(frac{1}m right) left(frac{m-1}n right)}{left(frac{m}n right)}
$$
I feel like I am misunderstanding how permutations are used in this situation, so any insights on how to solve this question would be appreciated.
A person is fixed in the committee, it must select $m-1$ from $n-1$ people, that is $dbinom{n-1}{m-1}$
The number of all cases, selecting $m$ people from $n$ is $dbinom{n}{m}$
$P=dfrac {dbinom{n-1}{m-1}}{dbinom{n}{m}}=dfrac{m}{n}$
Answered by Lion Heart on February 6, 2021
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