16 Mar 21
@joe-shmo saidWe could get very unlucky.
In a lecture of 100 students, the teacher pre-selects 8 books { A,B,C,D,E,F,G,H }. Each of the students is instructed to read 6 out of the 8 pre-selected books by the end of the term. At a minimum; how many times is the set of books {A,C,E,F,G,H} read?
If all 100 of them happen to pick C through H, then book A is never read, and the answer is 0.
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16 Mar 21
3 edits
@bigdoggproblem saidYou are correct! Not the question I actually wanted the answer to, but that is my fault ( tweaking problems has its downfalls ). I'm going to try and reformulate and ask another question.
We could get very unlucky.
If all 100 of them happen to pick C through H, then book A is never read, and the answer is 0.
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16 Mar 21
A better question...I hope ( should be, since I'm reposting it as I experienced it).
Students in a lecture are assigned to read 6 of 8 pre selected books from the instructor by the end of the term. At the end of the term, the instructor found that any selection of six books was read at most 4 times in the class. What is the maximum number of students that could be attending the class?
16 Mar 21
@joe-shmo said6 out of 8- 28 combinations
A better question...I hope ( should be, since I'm reposting it as I experienced it).
Students in a lecture are assigned to read 6 of 8 pre selected books from the instructor by the end of the term. At the end of the term, the instructor found that any selection of six books was read at most 4 times in the class. What is the maximum number of students that could be attending the class?
4*28 -112 students
17 Mar 21
@joe-shmo saidno of books 6 out of 8 =28
In a class of 100 students, what is the probability at least 4 students read books { A,B,C,E,G,H }?
no of students = 100
no of books read =4 out of 100 students
big numbers but the probability comes out at .0007.
Think I might have gone wrong somewhere!
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17 Mar 21
@venda saidI can't figure out your calculation, but its not correct. Perhaps try to answer the next question first ( sorry about the flipped chronology ) its crucial to answering this question.
no of books 6 out of 8 =28
no of students = 100
no of books read =4 out of 100 students
big numbers but the probability comes out at .0007.
Think I might have gone wrong somewhere!
What is the probability is that no one reads the set { A,B,C,E,G,H }?
17 Mar 21
@joe-shmo saidBit late now.
I can't figure out your calculation, but its not correct. Perhaps try to answer the next question first ( sorry about the flipped chronology ) its crucial to answering this question.
What is the probability is that no one reads the set { A,B,C,E,G,H }?
I'll have another think tomorrow.
If anyone else wants to answer,I don't mind
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18 Mar 21
@venda saidNo pressure. I'm just leaving some bread crumbs!
Bit late now.
I'll have another think tomorrow.
If anyone else wants to answer,I don't mind
18 Mar 21
@joe-shmo saidI got 2.6%, but I have trouble believing that answer.
I can't figure out your calculation, but its not correct. Perhaps try to answer the next question first ( sorry about the flipped chronology ) its crucial to answering this question.
What is the probability is that no one reads the set { A,B,C,E,G,H }?
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18 Mar 21
3 edits
@bigdoggproblem saidThat is correct. The probability of of no one reading that set is:
I got 2.6%, but I have trouble believing that answer.
P( n = 0 ) = ( 27/ 28 )^100 ≈ 2.6%
so the ball is rolling.
The next forward step would be to answer:
In a class of 100 students what is the probability that exactly "n" people read the set { A,B,C,E,G,H}?
18 Mar 21
1 edit
@joe-shmo saidSorry Joe,I seem to have lost this.
That is correct. The probability of of no one reading that set is:
P( n = 0 ) = ( 27/ 28 )^100 ≈ 2.6%
so the ball is rolling.
The next forward step would be to answer:
In a class of 100 students what is the probability that exactly "n" people read the set { A,B,C,E,G,H}?
I don't understand the equation.
Are you saying 27/28 to the power 100?
Also I don't see where 27 divided by 28 comes from.
Perhaps it's the way the question is posed.
Are you saying 1 book out of the set{abc etc) or all the books in set{abcetc)?