If you were to guess on every exam question (and assume that there are 4 answer choice and not 3 although we could solve it either way).
The probability of guessing 70/100 questions correct would by 100C70*.25^70*.75^(100-70).
Lets say 70% is a pass. Is the probability of passing then 100C70*.25^70*.75^(100-70) + 100C71*.25^71*.75^(100-71)+.......100C100*.25^100*.75^(100-100)?作者: soddy1979 时间: 2011-7-11 20:07
I think the formula is the sum of the probabilities of getting 70/100 + 71/100 + 72/100...100/100, where the (first) formula is .25^70*.75^30 and on and on.作者: kd26gioi 时间: 2011-7-11 20:07
There are 240 questions, not 100. The odds are zero.作者: disiz64 时间: 2011-7-11 20:07
Your formula is correct (this is easy to verify e.g. in Excel). The answer is 0.43*10^(-20).
Edited 1 time(s). Last edit at Wednesday, December 8, 2010 at 01:38PM by shootingstar.作者: lc26mizzou 时间: 2011-7-11 20:07
yeah i tried finding probability of passing cfa level 1 assuming 65% passing rate by guessing entire exam - it was 0 作者: kmf229 时间: 2011-7-11 20:07
no......the binomial we learned was to find the exact probability of choosing x out of n. I was trying to find the probability if choosing at least x (or more) out of n, which is different and hence the question.作者: bapswarrior 时间: 2011-7-11 20:07
use minitab CDF function (if u r familiar with program) or u will have to count probability of exact result for each one and then sum them up - hassle
