Turn on thread page Beta
    • Thread Starter
    Offline

    19
    ReputationRep:
    Pretty sure this is fairly simple and I'm just being a total idiot right now as I haven't done probability in ages, but can someone help me with this:

    "Suppose that I think the probability that a certain particle exists is 0.2. Furthermore my theory tells me that if the particle exists the probability that a certain experiment succeeds is 0.8, whereas if the particle doesn't exist the probability of success is 0.05. The experiment does succeed. How probable should I think it that the particle exists now?"

    How do I work out what the probability of the experiment succeeding, period, given nothing, is?
    Offline

    14
    ReputationRep:
    (Original post by TorpidPhil)
    Pretty sure this is fairly simple and I'm just being a total idiot right now as I haven't done probability in ages, but can someone help me with this:

    "Suppose that I think the probability that a certain particle exists is 0.2. Furthermore my theory tells me that if the particle exists the probability that a certain experiment succeeds is 0.8, whereas if the particle doesn't exist the probability of success is 0.05. The experiment does succeed. How probable should I think it that the particle exists now?"

    How do I work out what the probability of the experiment succeeding, period, given nothing, is?
    If E is the event "the particle exists" and X is the event "the experiment succeeds" then what you have been given is P(E), P(X|E) and P(X| ~E). You should now be able to work out P(X) by using the law of total probability.
    • Thread Starter
    Offline

    19
    ReputationRep:
    (Original post by Gregorius)
    If E is the event "the particle exists" and X is the event "the experiment succeeds" then what you have been given is P(E), P(X|E) and P(X| ~E). You should now be able to work out P(X) by using the law of total probability.
    Yeah, that's what I can't do because I suck at probability and it is making my mind trip up for no apparent reason :P
    Offline

    14
    ReputationRep:
    (Original post by torpidphil)
    yeah, that's what i can't do because i suck at probability and it is making my mind trip up for no apparent reason
    p(x) = p(x|e)p(e) + p(x|~e)p(~e)
    • Thread Starter
    Offline

    19
    ReputationRep:
    (Original post by Gregorius)
    p(x) = p(x|e)p(e) + p(x|~e)p(~e)
    Than you sir
 
 
 
Reply
Submit reply
Turn on thread page Beta
Updated: March 1, 2016
The home of Results and Clearing

1,272

people online now

1,567,000

students helped last year

University open days

  1. Bournemouth University
    Clearing Open Day Undergraduate
    Fri, 17 Aug '18
  2. University of Bolton
    Undergraduate Open Day Undergraduate
    Fri, 17 Aug '18
  3. Bishop Grosseteste University
    All Courses Undergraduate
    Fri, 17 Aug '18
Poll
Will you be tempted to trade up and get out of your firm offer on results day?
Useful resources

Make your revision easier

Maths

Maths Forum posting guidelines

Not sure where to post? Read the updated guidelines here

Equations

How to use LaTex

Writing equations the easy way

Student revising

Study habits of A* students

Top tips from students who have already aced their exams

Study Planner

Create your own Study Planner

Never miss a deadline again

Polling station sign

Thinking about a maths degree?

Chat with other maths applicants

Can you help? Study help unanswered threads

Groups associated with this forum:

View associated groups

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Write a reply...
Reply
Hide
Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.