Consider the following weighted averages of independent random variables X1, X2 , X3  all with mean µ and variance σ2 :  ˆθ1 = 1/3 X1 + 1/3 X2 + 1/3 X3    ˆθ2 = 1/4 X1 + 2/4 X2  + 1/4 X3  ˆθ3 = 2/5 X1  + 2/5 X2  + 2/5 X3  (a) Find E[ ˆθ1], E[ ˆθ2], and E[ ˆθ3]  (b) Are ˆθ1, ˆθ1, and ˆθ1 unbiased for µ? Please Explain.  (c) Find the variance for ˆθ1, ˆθ1, and ˆθ1 (d) If you had to use one of the above unbiased estimators, which would you pick? Explain.

Calculus For The Life Sciences
2nd Edition
ISBN:9780321964038
Author:GREENWELL, Raymond N., RITCHEY, Nathan P., Lial, Margaret L.
Publisher:GREENWELL, Raymond N., RITCHEY, Nathan P., Lial, Margaret L.
Chapter1: Functions
Section1.2: The Least Square Line
Problem 5E
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Consider the following weighted averages of independent random variables X1, X2 , X3  all with mean µ and variance σ2 :

 ˆθ1 = 1/3 X1 + 1/3 X2 + 1/3 X3  

 ˆθ2 = 1/4 X1 + 2/4 X2  + 1/4 X3 

ˆθ3 = 2/5 X1  + 2/5 X2  + 2/5 X3

 (a) Find E[ ˆθ1], E[ ˆθ2], and E[ ˆθ3]

 (b) Are ˆθ1, ˆθ1, and ˆθ1 unbiased for µ? Please Explain.

 (c) Find the variance for ˆθ1, ˆθ1, and ˆθ1

(d) If you had to use one of the above unbiased estimators, which would you pick? Explain.

***Note: Questions B and C are worded slightly different from similar problem showing in Chegg. So, please do not copy!    

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