variance-covariance matrix การใช้

• All these estimates are feasible unbiased estimates . we use the quotient of the determinant of the variance - covariance matrix of the feasible unbiased estimates , that is , a kind of relative efficency to compare these esti - mates . the results have instructive significance for practice
• Panel data model is an important linear model in economics , finance , biology , medicines and other fields . in recent twenty years , statistical in - ferrence about this model attracts many statisticians . in this paper , we first generalize the latest development of parameter estimation in this field , then focus on parameter estimation in the panel model with individual effect and time effect . many articles researched the parameter estimation of the regression coefficents in the case that both individual effect and time effect are random , but in some conditions , it is more reasonable if we suppose either of them is fixed . this paper is based on this hypothesis to research the estimations of the coefficents . the variance - covariance matrix still include parameter of variance in this condition , so our purpose is to look for feasible estimations
• Discusses the characteristic values on individual stock risk with the standard deviation , variance ( 2 ) , standard deviation coefficient ( cv ) and coefficient measurement , construct the individual on stock ' s statistics index system on investment risk . 2 . discuss the characteristic of standard deviation , variance , variance - covariance matrix to measure the investment risk of stock portfolio