hey /b/ I have an exam tomorrow
there are 5 questions given beforehand
three will be on the exam randomly selected
I must awnser two of the three
how many questions do I have to study for? what are the chances of a question I didn't study for showing up if I don't study them all?
I know this is some serious shit that might be out of Veeky Forums leauge
All of them
user the answer is all of them
I don't think that's how statistics work
>hey /b/
smooth
failed cunt. go bed.
pls exam is at 8:30am I only have 4 hours and I want to sleep because I have another exam I haven't studied for at 7pm and an essay to write as well as an exam tomorrow.
I need to know optimal study strats
If the questions are randomly selected there are 5!/2!3! ways to pick three. If you study only three questions you will have a 100% chance at getting two questions you studied and a 1/3 chance in getting a third question you studied for.
You should study for all them tho, unless you're ok with there being a 66% chance you will get a question you didn't study for
If I only have to answer 2 of the three why does it matter to have one I didn't study for show up?
I lied srry. You're guaranteed to get 1 question you studied and c(4,2)/c(5,3) for the other two
>c(4,2)/c(5,3) for the other two
what do you mean by this
I mean if you study three questions there is a 100% chance you'll get 1 question you studied and a 60% chance the other two questions will be ones you studied
it depends. If it's a math exam, all of them. If it's a physics exam, then all of them. If it's a chem exam, then I would probably go with all of them. But if it's a biology exam, then you might want to be a little conservative and do all of them.
what is the chance of only 1 other question being what I studied?
again I stress I only have to answer two of the three randomly selected questions.
what the notation is for "combinations" in combinations, which is similar to a permutation, except order matters in permutations but not combinations.
You've got to study four questions. Since you only miss one of them, you can always answer two of the three, whichever you got.
statistically what are my chances of getting two I don't know if I only study three?
someone just give the poor faggot the distribution already
study 2: 10% chance of 0 showing up, 60% chance of 1 showing up, 30% chance of both showing up
study 3: 30% chance of 1 showing up, 60% chance of 2 showing up, (10% chance of 3 showing up)
study 4: 60% chance of 2 showing up, (40% chance of 3 showing up)
study 5: who gives a shit, he's clearly under time pressure
>60% chance of two showing up
wait really? I thought I has a 100% chance of getting two if I study four.
How does 3 and 4 both have a 60% chance of two showing up?
Guess I should have been clearer with the terminology.
"X showing up" means that the test will have X questions that you studied for.
So
60% chance that you studied for exactly 2 of the problems, and 40% chance that you studied for all 3 of them.
that's just the way it is m8
the difference is that if you study 4 you are 100% safe even if the 60% event doesn't happen, whereas if you only study 3 you have a high chance of getting screwed if you're unlucky.
Because he's a dumb faggot who doesn't know simple probability or how to set his sample space.
If you study 3 there's a 100% chance you get one, and a 1/4 chance you'll get a second, and 1/4 chance you'll get a third and a 1/16 chance you'll get both
so does that mean I have a 50% chance of getting two questions I know if I study three?
>study 3: 30% chance of 1 showing up, 60% chance of 2 showing up, (10% chance of 3 showing up)
study 4: 60% chance of 2 showing up, (40% chance of 3 showing up)
Is this that common core math i've heard so much about?
If you study three you'll get 1 and there's a 50/50 you'll get the other two. You can prove this with a Venn diagram
I only need one of the other two though. I don't care if a question I didn't study for shows up, only if two I didn't study for show up.
You're still here, what the fuck
Here, let me rewrite the distribution in study 1: 60% chance that it shows up
study 2: 90% chance of at least 1 showing up, 30% of both showing up
study 3: 100% chance of at least 1 showing up, 70% chance of at least 2 showing up, 10% chance of all 3 showing up
study 4: 100% chance of at least 2 showing up, 40% chance of 3 showing up
if you study 3 you could still get 5-3=2 unknown ones which could fail you since 3-2=1