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CTO
Joined: 19 Dec 2002
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If we want a chance of 5% or less that a person will [#permalink]
 28 Apr 2003, 11:20
If we want a chance of 5% or less that a person will encounter any question twice (in first and second test) in two consequtive random selections of 40 questions out of a question bank, how large should this question bank be?
I fear you need Excel to solve this one.
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SVP
Joined: 03 Feb 2003
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x is the number of questions in the bank. The probability of having at least one question in two selections of 40 = 1 - [(x-40)C40/xC40]
It should be less than or equal to 0.05.
1 - [(x-40)C40/xC40]<=0.05
Excel says that x should be about 31000. P=0.0503.
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CTO
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21 years to develop [#permalink]
06 May 2003, 04:26
thanks 
Right now we have capacity of 4 questions a day, which means developing such a bank will take 21 years.
Ok, this means we need software that would remember which questions you already answered...
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SVP
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The number of questions in your bank should increse exponentially. In this case it should take much less time. :D
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CTO
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Great idea, stolyar!
If bb got $1 mln, we could launch a campaign - get $10 for every question you prepared, + $1 for each question your friends prepared, so that people could use a multi-level marketing, to get an exponent
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Founder
Status: On Vacation :-)
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gravedigger wrote: Great idea, stolyar! If bb got $1 mln, we could launch a campaign - get $10 for every question you prepared, + $1 for each question your friends prepared, so that people could use a multi-level marketing, to get an exponent Great Idea. I really love it... can we drop the second part and leave me with $1 mln?
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close
