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

    0
    ReputationRep:
    I'm a tad stuck on this question and was wondering if anyone could help me out with a step by step example? Thankyou!

    The random variable T has a mean of 20 and a standard deviation of 5.
    It is required to scale T by using the transformation S = 3T + 4
    Find E(S) and Var(S)
    Offline

    20
    ReputationRep:
    it sounds more like S1 or S2 than C2 ?
    Online

    22
    ReputationRep:
    (Original post by Kaylalou_21)
    I'm a tad stuck on this question and was wondering if anyone could help me out with a step by step example? Thankyou!

    The random variable T has a mean of 20 and a standard deviation of 5.
    It is required to scale T by using the transformation S = 3T + 4
    Find E(S) and Var(S)
    E(3T +4) = E(3T) + 4 = 3E(T)

    Var(3T+4) = Var(3T) = 3^2Var(T) = 9Var(T)

    You know E(T) = 20 and Vart(T) = 5^2 = 25.
    Offline

    20
    ReputationRep:
    i f Y = 5X - 4

    then E(Y) = 5E(X) - 4

    & Var(Y) = 25Var(X)
    Online

    22
    ReputationRep:
    Oh, and I'm moving this to maths (and correcting the title to S2, which is what I think you mean).
    • Thread Starter
    Offline

    0
    ReputationRep:
    (Original post by the bear)
    it sounds more like S1 or S2 than C2 ?
    Oops typo, it is S1
    • Thread Starter
    Offline

    0
    ReputationRep:
    (Original post by Zacken)
    E(3T +4) = E(3T) + 4 = 3E(T)

    Var(3T+4) = Var(3T) = 3^2Var(T) = 9Var(T)

    You know E(T) = 20 and Vart(T) = 5^2 = 25.
    Thankyou, this was really helpful and I apologise I just joined so I'm not quite sure how to navigate this site properly yet haha
    Online

    22
    ReputationRep:
    (Original post by Kaylalou_21)
    Thankyou, this was really helpful and I apologise I just joined so I'm not quite sure how to navigate this site properly yet haha
    Glad it was helpful, don't worry about it - just remember that in the future, maths questions go in maths study help. :-)
 
 
 
  • 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
    Would you rather give up salt or pepper?
    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

    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.