# probability of passing

*this question is simply to to understand statistics, not realy to figure out how much of the program to study.

assume the CFA level I exam has 400 LOS

CFA institute will test 120 questions which for simplicity here we assume each will come from a different LOS

Assume a student either knows an LOS or does not, binary, if he knows it he will answer correct, else her will answer wrrong.

How do you calculate the probability of the student passing the exam given that he knows a certain number of LOS?

If he knows 70% of LOS, is the probability of him getting a 70 or more on the exam calculate using binomial formula, 120 trials, 0.7 chance of success, and calculating the probability of scoring above 84 or above correct yeilding 54%?

*if correct, how do you think removing the condition of only one question per los changes the results, would it bias it more towards making the test easier to pass cause if an los shows up more than once he gets double points, and he is more likely to know the los than not ? or would it not change anything

Many thanks

C

STL, times have changed.

B is the NEW choice C now

Too much thinking for a Friday. It is neither B nor C, it’s the longest answer.

if each question comes from a different LOS, you are sampling without replacement. your population has size 400 with 70%*400=280 successes in it. you have 120 trials without replacement - use hypegeometric, not binomial.

if you remove the condition of only one question per LOS, then you are sampling with replacement and can use the binomial as you did before. both will give you fairly similar answers

Disagree with all of the above. The correct choice is the answer with the most commas and semicolons. You gotta watch those tricky twists and turns, they’re gonna throw most candidates.

The question clearly doesn’t have enough double and triple negatives to be an official CFAI question. Did you get this from the qbank?

hey lostcfa,

I haven’t taken level 3 yet, but i can confirm A has the highest probability of being correct on level 2. So be sure to factor that in.

(i put down A LOT of A’s and passed)

240 questions

Nothing ventured, nothing gained.