Hey there! Sign in to join this conversationNew here? Join for free
    • Thread Starter
    Offline

    2
    ReputationRep:
    4 options 30 questions. he wants the probability of someone passing the test by guessing the answer to each question to be 10% or less. what is the lowest score that should be set as the pass mark?

    If anyone could help it would be great
    • TSR Support Team
    • Study Helper
    Offline

    20
    ReputationRep:
    (Original post by Morgan111)
    4 options 30 questions. he wants the probability of someone passing the test by guessing the answer to each question to be 10% or less. what is the lowest score that should be set as the pass mark?

    If anyone could help it would be great
    Can you please post your thoughts and all your working?
    • Thread Starter
    Offline

    2
    ReputationRep:
    I know X~B(30,0.25) letting X be the probability that a student gets a question right by guessing.

    And that it’s asking for P(X<x) <0.1 but I don’t know where to go from there.
    Posted on the TSR App. Download from Apple or Google Play
    • TSR Support Team
    • Study Helper
    Offline

    20
    ReputationRep:
    (Original post by Morgan111)
    I know X~B(30,0.25) letting X be the probability that a student gets a question right by guessing.

    And that it’s asking for P(X<x) <0.1 but I don’t know where to go from there.
    Are you doing old spec or new spec A Level?

    You could either use a calculator to try different values of x until you get < 0.1. Or you could use probability tables which may be quicker if you've used them before?
    • Thread Starter
    Offline

    2
    ReputationRep:
    Ok thank you ☺️ can’t believe I didn’t think of that !
    (And old spec)
    Posted on the TSR App. Download from Apple or Google Play
 
 
 
  • See more of what you like on The Student Room

    You can personalise what you see on TSR. Tell us a little about yourself to get started.

  • Poll
    Did TEF Bronze Award affect your UCAS choices?
    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
  • See more of what you like on The Student Room

    You can personalise what you see on TSR. Tell us a little about yourself to get started.

  • 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

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