VARIANCE COMPONENT ESTIMATION TECHNIQUES COMPARED FOR 2 MATING DESIGNS WITH FOREST GENETIC ARCHITECTURE THROUGH COMPUTER-SIMULATION

Computer simulation was used to compare minimum variance quadratic est imation (MIVQUE), minimum norm quadratic unbiased estimation (MINQUE), restricted maximum likelihood (REML), maximum likelihood (ML), and He nderson's Method 3 (HM3) on the basis of variance among estimates, mea n square error (MSE), bias and probability of nearness for estimation of both individual variance components and three ratios of variance co mponents. The investigation also compared three procedures for dealing with negative estimates and included the use of both individual obser vations and plot means as the experimental unit of the analysis. The s tructure of data simulated (field design, mating designs, genetic arch itecture and imbalance) represented typical analysis problems in quant itative forest genetics. Results of comparing the estimation technique s demonstrated that: estimates of probability of nearness did not disc riminate among techniques; bias was discriminatory among procedures fo r dealing with negative estimates but not among estimation techniques (except ML); sampling variance among estimates was discriminatory amon g procedures for dealing with negative estimates, estimation technique s and unit of observation; and MSE provided no additional information to variance of the estimates. HM3 and REML were the closest competitor s under these criteria; however, REML demonstrated greater robustness to imbalance. Of the three negative estimate procedures, two are of pr actical significance and guidelines for their application are presente d. Estimates from individual observations were always preferable to th ose from plot means over the experimental levels of this study.