Got Homework?
Connect with other students for help. It's a free community.
Here's the question you clicked on:
 0 viewing
sleung
Group Title
A student who is taking a 30 question multiple choice test knows 24 of the answers. If the student doesn't know the answer, he chooses uniformly from 1 of 5 choices. Given that he gets a randomly chosen question right, what is the probability he guessed on the question?
 5 months ago
 5 months ago
sleung Group Title
A student who is taking a 30 question multiple choice test knows 24 of the answers. If the student doesn't know the answer, he chooses uniformly from 1 of 5 choices. Given that he gets a randomly chosen question right, what is the probability he guessed on the question?
 5 months ago
 5 months ago

This Question is Open

elvisg1993 Group TitleBest ResponseYou've already chosen the best response.0
30!/(24!) * 1/5
 5 months ago

sleung Group TitleBest ResponseYou've already chosen the best response.0
How'd you get that elvis?
 5 months ago

dumbcow Group TitleBest ResponseYou've already chosen the best response.1
conditional probability \[P(A  B) = \frac{P(A and B)}{P(B)}\] probability he guesses and gets it right = 1/5 probability the question is right = (24+6/5)/30
 5 months ago

sleung Group TitleBest ResponseYou've already chosen the best response.0
My exam says that the answer is 1/21. How do u get that?
 5 months ago

dumbcow Group TitleBest ResponseYou've already chosen the best response.1
oh sorry my P(AB) is wrong, it should be 1.2/30 \[\frac{\frac{1.2}{30}}{\frac{25.2}{30}} = \frac{1.2}{25.2} = \frac{1}{21}\]
 5 months ago

sleung Group TitleBest ResponseYou've already chosen the best response.0
Thanks a lot.
 5 months ago

sleung Group TitleBest ResponseYou've already chosen the best response.0
How'd you get 1.2 and 25.2? Still not quite clear on that.
 5 months ago

dumbcow Group TitleBest ResponseYou've already chosen the best response.1
1.2 is the avg number of questions guessed correctly > 6*(1/5) 25.2 is avg total num of correct questions > 24 + 6/5
 5 months ago

sleung Group TitleBest ResponseYou've already chosen the best response.0
Thanks so much
 5 months ago

sleung Group TitleBest ResponseYou've already chosen the best response.0
For 0<x<y<z<1, the joint density of (X,Y,Z) is given by f(x,y,z)=48xyz. Find P(Y>1/2). I got .78, but my exam says it's .84.
 5 months ago

dumbcow Group TitleBest ResponseYou've already chosen the best response.1
\[48 \int\limits_.5^1 \int\limits_y^1 \int\limits_0^y (xyz) dx dz dy\] \[= 48 \int\limits_.5^1 \int\limits_y^1 \frac{y^3 z}{2} dz dy\] \[= 48 \int\limits_.5^1 (\frac{y^3}{4}  \frac{y^5}{4}) dy\] \[= 12(\frac{y^4}{4}  \frac{y^6}{6}) _.5^1\] \[= 1  \frac{10}{64} = \frac{27}{32}\] = 0.84375
 5 months ago

dumbcow Group TitleBest ResponseYou've already chosen the best response.1
how did you go from precalc probability to multivariable calculus?? lol
 5 months ago

sleung Group TitleBest ResponseYou've already chosen the best response.0
Haha, don't know  guess i should've asked that in the calc section. I was asked to find a probability though.
 5 months ago

sleung Group TitleBest ResponseYou've already chosen the best response.0
Insurance losses L in a given year have a lognormal distribution with L=e^X, where X is a normal random variable with mean 3.9 and standard deviation 0.8. If a $100 deductible and a $50 benefit are imposed, what is the probability the insurance company will pay the benefit limit given that a loss exceeds the deductible?
 5 months ago

sleung Group TitleBest ResponseYou've already chosen the best response.0
A fair 6sided die is rolled 1,000 times. Using a normal approximation with a continuity correction, what is the probability the number of 3's rolled is greater than 150 and less than 180? I'm supposed to get .78, but instead I'm getting .81.
 5 months ago
See more questions >>>
Your question is ready. Sign up for free to start getting answers.
spraguer
(Moderator)
5
→ View Detailed Profile
is replying to Can someone tell me what button the professor is hitting...
23
 Teamwork 19 Teammate
 Problem Solving 19 Hero
 Engagement 19 Mad Hatter
 You have blocked this person.
 ✔ You're a fan Checking fan status...
Thanks for being so helpful in mathematics. If you are getting quality help, make sure you spread the word about OpenStudy.