North Eastern Hill University

About: North Eastern Hill University is a education organization based out in Shillong, Meghalaya, India. It is known for research contribution in the topics: Population & Catalysis. The organization has 2318 authors who have published 4476 publications receiving 48894 citations.

Least absolute deviation estimation of linear econometric models: a literature review

Abstract: Econometricians generally take for granted that the error terms in the econometric models are generated by distributions having a finite variance However, since the time of Pareto the existence of error distributions with infinite variance is known Works of many econometricians, namely, Meyer & Glauber (1964), Fama (1965) and Mandlebroth (1967), on economic data series like prices in financial and commodity markets confirm that infinite variance distributions exist abundantly The distribution of firms by size, behaviour of speculative prices and various other recent economic phenomena also display similar trends Further, econometricians generally assume that the disturbance term, which is an influence of innumerably many factors not accounted for in the model, approaches normality according to the Central Limit Theorem But Bartels (1977) is of the opinion that there are limit theorems, which are just likely to be relevant when considering the sum of number of components in a regression disturbance that leads to non-normal stable distribution characterized by infinite variance Thus, the possibility of the error term following a non-normal distribution exists The Least Squares method of estimation of parameters of linear (regression) models performs well provided that the residuals (disturbances or errors) are well behaved (preferably normally or near-normally distributed and not infested with large size outliers) and follow Gauss-Markov assumptions However, models with the disturbances that are prominently non-normally distributed and contain sizeable outliers fail estimation by the Least Squares method An intensive research has established that in such cases estimation by the Least Absolute Deviation (LAD) method performs well This paper is an attempt to survey the literature on LAD estimation of single as well as multi-equation linear econometric models

Microbial enzyme activities related to litter decomposition near a highway in a sub-tropical forest of North East India

Abstract: Cellulose, amylase and invertase activities were studied in extracts of leaf litters of Alnus nepalensis and Pinus kesiya during litter decomposition at a roadside (more polluted) and a non-roadside (less polluted) forest stand. Enzyme activities were considerably higher in litter at the less polluted than at the more polluted site. Cellulase and amylase activities showed a marked seasonal variation at both sites. Cellulase and amylase activities increased during litter decomposition, whereas invertase activity was higher at the begining of litter decomposition. Invertase activity correlated positively with litter soluble sugars. Cellulase and amylase activities, but not invertase activity, were correlated significantly with numbers of fungi and bacteria.