A Comparative Efficiency Analysis of Wheat Farms using Parametric and Nonparametric Methods

Efficiency Analysis, Deterministic Nonparametric Method, Parametric, Stochastic Frontier., Production Economics, Q12,

Examining the Reliability of Logistic Regression Estimation Software

Research Methods/ Statistical Methods,

Spatiotemporal Difference-in-Differences: A Dynamic Mechanism of Socio-Economic Evaluation

Advances in econometric modeling and analysis of spatial cross-sectional and spatial panel data assist in revealing the spatiotemporal characteristics behind socio-economic phenomena and improving prediction accuracy. Difference-in-differences (DID) is frequently used in causality inference and estimation of the treatment effect of the policy intervention in different time and space dimensions. Relying on flexible distributional hypotheses of treatment versus experiment groups on spillover, spatiotemporal DID provides space for innovation and alternatives, given the spatial heterogeneity, dependence, and proximity into consideration. This chapter gives a practical econometric evaluation of the dynamic mechanism in this spatiotemporal context as well as a toolkit for this fulfillment

On the examination of the reliability of statistical software for estimating regression models with discrete dependent variables

The numerical reliability of statistical software packages was examined for logistic regression models, including SAS 9.4, MATLAB R2015b, R 3.3.1., Stata/IC 14, and LIMDEP 10. Thirty unique benchmark datasets were created by simulating alternative conditional binary choice processes examining rare events, near-multicollinearity, quasi-separation and nonlinear transformation of variables. Certified benchmark estimates for parameters and standard errors of associated datasets were obtained following standards set-out by the National Institute of Standards and Technology. The logarithm of relative error was used as a measure of accuracy for numerical reliability. The paper finds that choice of software package and procedure for estimating logistic regressions will impact accuracy and use of default settings in these packages may significantly reduce reliability of results in different situations

45S rDNA Regions Are Chromosome Fragile Sites Expressed as Gaps In Vitro on Metaphase Chromosomes of Root-Tip Meristematic Cells in Lolium spp

BACKGROUND: In humans, chromosome fragile sites are regions that are especially prone to forming non-staining gaps, constrictions or breaks in one or both of the chromatids on metaphase chromosomes either spontaneously or following partial inhibition of DNA synthesis and have been well identified. So far, no plant chromosome fragile sites similar to those in human chromosomes have been reported. METHODS AND RESULTS: During the course of cytological mapping of rDNA on ryegrass chromosomes, we found that the number of chromosomes plus chromosome fragments was often more than the expected 14 in most cells for Lolium perenne L. cv. Player by close cytological examination using a routine chromosome preparation procedure. Further fluorescent in situ hybridization (FISH) using 45S rDNA as a probe indicated that the root-tip cells having more than a 14-chromosome plus chromosome fragment count were a result of chromosome breakage or gap formation in vitro (referred to as chromosome lesions) at 45S rDNA sites, and 86% of the cells exhibited chromosome breaks or gaps and all occurred at the sites of 45S rDNA in Lolium perenne L. cv. Player, as well as in L. multiflorum Lam. cv. Top One. Chromatin depletion or decondensation occurred at various locations within the 45S rDNA regions, suggesting heterogeneity of lesions of 45S rDNA sites with respect to their position within the rDNA region. CONCLUSIONS: The chromosome lesions observed in this study are very similar cytologically to that of fragile sites observed in human chromosomes, and thus we conclude that the high frequency of chromosome lesions in vitro in Lolium species is the result of the expression of 45S rDNA fragile sites. Possible causes for the spontaneous expression of fragile sites and their potential biological significance are discussed

A comparative efficiency analysis of wheat farms using parametric and nonparametric methods

This study examined whether the efficiency measures were invariant to choice of parametric and nonparametric methods for a sample of 183 wheat farms. The efficiency measures from the deterministic parametric method were smaller than those from the deterministic method. There was a trade-off between scale efficiency and economic efficiency. In the deterministic nonparametric method, the economic efficiency, scale efficiency and overall efficiency results were invariant to the number of inputs or the dimensionality. Only allocative and pure technical efficiency measures depended on the dimensionality. This work illustrated the importance of holding curvature for the cost function in stochastic frontier results

Examining the reliability of logistic regression estimation software

Doctor of PhilosophyDepartment of Agricultural EconomicsAllen M. FeatherstoneBryan W. SchurleThe reliability of nine software packages using the maximum likelihood estimator for the logistic regression model were examined using generated benchmark datasets and models. Software packages tested included: SAS (Procs Logistic, Catmod, Genmod, Surveylogistic, Glimmix, and Qlim), Limdep (Logit, Blogit), Stata (Logit, GLM, Binreg), Matlab, Shazam, R, Minitab, Eviews, and SPSS for all available algorithms, none of which have been previously tested. This study expands on the existing literature in this area by examination of Minitab 15 and SPSS 17. The findings indicate that Matlab, R, Eviews, Minitab, Limdep (BFGS), and SPSS provided consistently reliable results for both parameter and standard error estimates across the benchmark datasets. While some packages performed admirably, shortcomings did exist. SAS maximum log-likelihood estimators do not always converge to the optimal solution and stop prematurely depending on starting values, by issuing a ``flat" error message. This drawback can be dealt with by rerunning the maximum log-likelihood estimator, using a closer starting point, to see if the convergence criteria are actually satisfied. Although Stata-Binreg provides reliable parameter estimates, there is no way to obtain standard error estimates in Stata-Binreg as of yet. Limdep performs relatively well, but did not converge due to a weakness of the algorithm. The results show that solely trusting the default settings of statistical software packages may lead to non-optimal, biased or erroneous results, which may impact the quality of empirical results obtained by applied economists. Reliability tests indicate severe weaknesses in SAS Procs Glimmix and Genmod. Some software packages fail reliability tests under certain conditions. The finding indicates the need to use multiple software packages to solve econometric models

A Comparative Efficiency Analysis of Wheat Farms using Parametric and Nonparametric Methods

This study examined whether cost efficiency measures were invariant to the choice of parametric and nonparametric methods for a sample of 183 wheat farms. Discrepancies occurred when different methods were used. This work also illustrated the importance of imposing curvature of the cost function for stochastic frontier