Suppose that X1 and X2 are independent random variables having a common mean μ. Suppose al...

Suppose that X1 and X2 are independent random variables having a common mean μ. Suppose also that  and . The value of μ is unknown, and it is proposed that μ be estimated by a weighted average of X1 and X2. That is, will be used as an estimate of μ for some appropriate value of λ. Which value of λ yields the estimate having the lowest possible variance? Explain why it is desirable to use this value of λ.