Turn on thread page Beta
    • Thread Starter
    Offline

    0
    ReputationRep:
    A S2 question need help with. candidate picks his answer to each question at random from list of 3 answers with only 1 being correct. a candidate answering 18 or more questions correctly passes the examination.

    it is required that prob that candidate passes is less than 0.005. use a normal approximation to show that the paper should contain at most 31 questions...

    im just getting confused by whole question...need help please asap...thanx
    Offline

    0
    ReputationRep:
    (Original post by nacero2000)
    A S2 question need help with. candidate picks his answer to each question at random from list of 3 answers with only 1 being correct. a candidate answering 18 or more questions correctly passes the examination.

    it is required that prob that candidate passes is less than 0.005. use a normal approximation to show that the paper should contain at most 31 questions...

    im just getting confused by whole question...need help please asap...thanx
    weird hour of the day to be doing S2 - i remember doing that somewhere...
    here it is:ex 3b q 8b)?

    P(X>17.5)<0.005 where Y~N(np, npq)
    17.5-np/rt(npq) <-2.5758
    (17.5-np)^2 < 6.6347(npq)
    306.25-35np+(np)^2 <1.474n
    solving for n

    n=31.9 or 86.35 therefore:
    n<31.9 ir n<86.35

    n<31.9 satisfies both equations therefore as n is an integer, n =31 questions

    not re-read the question - just typing up my solution

    hope th is helps,
    Phil
 
 
 
Turn on thread page Beta
Updated: June 11, 2005
The home of Results and Clearing

1,012

people online now

1,567,000

students helped last year

University open days

  1. Keele University
    General Open Day Undergraduate
    Sun, 19 Aug '18
  2. University of Melbourne
    Open Day Undergraduate
    Sun, 19 Aug '18
  3. Sheffield Hallam University
    City Campus Undergraduate
    Tue, 21 Aug '18
Poll
A-level students - how do you feel about your results?
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.