Part of coniferous forests 280 trees of the same species and of similar ages. A preliminary estimate is required of the total weight of timber that trees will yield. A forestry expert claims to be able to make fairly accurate assessments of the yield from any tree merely by visual inspection, and makes such assessments for all 280 trees. He assesses the total yield as 439.5 tonnes. Subsequently, 25 trees picked at random are felled and their timber yields y; and their corresponding assessed yields, m, provide the following summary results. 25 M i=1 x2 = 73.47, _ Tiyi = 70.64, >Ti = 41.4 25 i=1Vi = 39.8 Ely, = 69.08 Estimate the total yield using either the ratio regression estimator, whichever seems most appropriate. Compare the efficiencies of ratio es- timator , the regression estimator, and the estimator based on the sample of y values alone