Two surveys were independently conducted to estimate a population mean, μ. Denote the estimates and their standard errors by X1 and X2 and σX1 and σX2 . Assume that X1 and X2 are unbiased. For some α and β, the two estimates can be combined to give a better estimator: X = αX1 + βX2 a. Find the conditions on α and β that make the combined estimate unbiased. b. What choice of α and β minimizes the variances, subject to the condition of unbiasedness?

Which option identifies how kevin should proceed in the following scenario? four years ago kevin designed an mp3 player for young children. now that technology has changed, he would like to update his design to ensure that it encompasses cutting-edge techniques. by creating a third-angle projection of his ideas by designing an isometric projection of his new ideas by referring to past designs and illustrations of his original model by conferring with engineers who have improved upon similar devices