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

    0
    ReputationRep:
    A random sample (X1, X2, X3...Xn) is taken from a population of unknown mean \mu and variance \sigma^2

    I have to find the bias of \mu* where \mu*= 	\sum Xi / (n-1)

    The bias is = E\mu*- \mu* , right?
    So I have:  1/(n-1) E( \sum Xi)- \sum Xi / (n-1)

    But I'm not really sure what to do after that? I have to find the variance and mse as well after but need the bias first...

    Any help appreciated, my stats lecturer is terrible and I've never done this topic before

    cheers!
    Offline

    15
    ReputationRep:
    (Original post by narc)
    The bias is = E\mu*- \mu* , right?
    No, it's E(mu*) - mu.

    So I have:  1/(n-1) E( \sum Xi)- \sum Xi / (n-1)
    Well, the hard part is working out E( \sum X_i) right? So why don't you think about what the sum of X_i is?

    \sum X_i = X_1 + X_2 + ... X_n surely?

    So you need to work out E(\mu*) = \frac{1}{n-1}E(\sum X_i) = \frac{1}{n-1}E(X_1 + X_2 + ... + X_n)
    • Thread Starter
    Offline

    0
    ReputationRep:
    (Original post by Swayum)
    No, it's E(mu*) - mu.



    Well, the hard part is working out E( \sum X_i) right? So why don't you think about what the sum of X_i is?

    \sum X_i = X_1 + X_2 + ... X_n surely?

    So you need to work out E(\mu*) = \frac{1}{n-1}E(\sum X_i) = \frac{1}{n-1}E(X_1 + X_2 + ... + X_n)
    Hmm, do I assume that  E X_i = \mu because the sample is random?
    Offline

    15
    ReputationRep:
    I have no clue to be honest.
    • Thread Starter
    Offline

    0
    ReputationRep:
    Ah. Well...thank you anyway
 
 
 
Poll
Do you agree with the PM's proposal to cut tuition fees for some courses?
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.