random variables with the same mean µ but possibly different variances σx2 and σy2. Imagine that X and Y  are the averages of independent samples of size n1 and n2, respectively, taken from populations with the same mean µ and the same variance σ2.  Apply below to identify the α that minimizes  and the minimum value.  Be sure to simplify both the new estimator and the minimum variance.  Interpret the result. The variance of αX+(1-α)Y, which

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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Suppose X and Y are independent random variables with the same mean µ but possibly different variances σx2 and σy2.

Imagine that X and Y  are the averages of independent samples of size n1 and n2, respectively, taken from populations with the same mean µ and the same variance σ2

Apply below to identify the α that minimizes  and the minimum value.  Be sure to simplify both the new estimator and the minimum variance.  Interpret the result.

The variance of αX+(1-α)Y, which also has mean µ, is minimized with α=σy2/(σX2y2).

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