Propensity Score Matching Methods for Non-experimental Causal Studies

This paper considers causal inference and sample selection bias in non-experimental settings in which: (i) few units in the non-experimental comparison group are comparable to the treatment units, and (ii) selecting a subset of comparison units similar to the treatment units is difficult because units must be compared across a high-dimensional set of pre-treatment characteristics. We propose the use of propensity score matching methods and implement them using data from the NSW experiment. Following Lalonde (1986), we pair the experimental treated units with non-experimental comparison units from the CPS and PSID and compare the estimates of the treatment effect obtained using our methods to the benchmark results from the experiment. We show that the methods succeed in focusing attention on the small subset of the comparison units comparable to the treated units and, hence, in alleviating the bias due to systematic differences between the treated and comparison units.

Causal Effects in Non-Experimental Studies: Re-Evaluating the Evaluation of Training Programs

This paper uses propensity score methods to address the question: how well can an observational study estimate the treatment impact of a program? Using data from Lalonde's (1986) influential evaluation of non-experimental methods, we demonstrate that propensity score methods succeed in estimating the treatment impact of the National Supported Work Demonstration. Propensity score methods reduce the task of controlling for differences in pre-intervention variables between the treatment and the non-experimental comparison groups to controlling for differences in the estimated propensity score (the probability of assignment to treatment, conditional on covariates). It is difficult to control for differences in pre-intervention variables when they are numerous and when the treatment and comparison groups are dissimilar, whereas controlling for the estimated propensity score, a single variable on the unit interval, is a straightforward task. We apply several methods, such as stratification on the propensity score and matching on the propensity score, and show that they result in accurate estimates of the treatment impact.

Measuring the effect of customer relationship management (CRM) components on the non financial performance of commercial banks: Egypt case

This paper presents customer relationship management (CRM) components as applied on the Egyptian Commercial Banks, examined from the bankers' point of view. Then, it intends to measure their effect on the level of customer satisfaction and loyalty from the customers’ point of view as examples of the non financial performance measures. The paper is quantitative in nature and consists of two different structured questionnaires using convenience/quota sampling. The first involved 180 employees in order to measure CRM applicability, and the second involved 270 customers to measure the level of customer satisfaction and loyalty and their effect on the Egyptian Commercial Banks' financial performance The findings show that the selected banks apply CRM components but the level of application differs from one bank to another. The results showed a significant positive relationship between CRM and customer satisfaction in the Egyptian Commercial Banks, when applying them together and not separately. In addition, there is a strong positive effect between customer satisfaction and loyalty which was reflected on the Commercial Banks' financial performance. The findings confirm the importance of studying and implementing CRM to achieve customer loyalty and improve the Egyptian Commercial Banks financial performance. Banks wishing to improve their relationships with customers need to focus on the CRM components to develop relevant and effective marketing strategies and tactics. The paper measures the CRM as a multidimensional construct as applied on the Egyptian Commercial Banks and relate it to the achievement of the ultimate goal of retaining customers to gaining a sustainable competitive advantage and achieve more profits

Influence of the Polarity of the Electric Field on Electrorheometry

Uniaxial extensional flow is a canonical flow typically used in rheological characterization to provide complementary information to that obtained by imposing simple shear flow. In spite of the importance of having a full rheological characterization of complex fluids, publications on the rheological characterization of mobile liquids under extensional flow have increased significantly only in the last 20 years. In the case of the rheological characterization of electrorheological fluids, the situation is even more dramatic, as the ERFs have been exclusively determined under simple shear flow, where an electrorheological cell is attached to the rotational rheometer generating an electric field perpendicular to the flow direction and that does not allow for inverting the polarity. The very recent work published by Sadek et al., who developed a new electrorheological cell to be used with the commercial Capillary Breakup Extensional Rheometer (CaBER), allows for the very first time performing electrorheometry under extensional flow. By means of the same experimental setup, this study investigates the influence of the polarity of the imposed electric field on the filament thinning process of a Newtonian and an electrorheological fluid. Results show that a polarity against the gravity results in filament thinning processes that live longer or reach a stable configuration at lower intensities of the applied electric field

Propensity Score Matching Methods for Non-Experimental Casual Studies

This paper considers casual inference and sample selection bias in non-experimental settings in which: (i) few unites in the non-experimental comparison group are comparable to treatment units; and (ii) selecting a subset of comparison units similar to the treatment units is difficult because units must be compared across a high-dimensional set of pre-treatment characteristics. We propose the use of propensity score matching methods, and implement them using data from the NSW experiment. Following Lalonde (1986), we pair the experimental treated units with non-experimental comparison units from the CPS and PSID, and compare the estimates of the treatment effect obtained using out methods to the benchmark results from the experiment. We show that the methods succeed in focusing attention on the small subset of the comparison units comparable to the treated units and, hence, in alleviating the bias due to systematic differences between the treated and comparison units

Conductance of S-Alkylisothiouronium Iodides in Methanol at 25° C

Equivalent conductivities are reported for S-Methyl-, S-n- . -Butyl, S-n-Amyl- and S-n-Heptylisothiouronium iodides in methanol (D = 32.63) at 25 °c. The data were analyzed by the Fuoss-Onsager equation for 1 : 1 associated electrolytes. The characteristic constants: the equivalent conductance at infinite dilution A0 , the closest approach distance a0 and the association constant KA are · derived

Spectrophotometric Study of Acid-Base Equilibria in Non-Aqueous Solvents

The equilibrium constants for the reaction of 2,6-dichloro-4- -nitrophenol, 2,6-dinitrophenol, 2,5-dinitrophenol and 2,4-dinitrophenol with some aliphatic amines of different structures have been determined spectrophotometrically in chlorobenzene, ethyl acetate and carbon tetrachloride as solvents. The data show that such reactions in inert solvents lead essentially to ion-pairs of the type BH+ ... A- where, HA and B represent the phenol and ·amine molecule, respectively. This conclusions was found to be in agreement with that obtained by other workers. In chlorobenzene as a solvent, the basic strengths fall in the order mono < di- < tri-n- . -butyl amine, while in ethyl acetate the order of basic strengths becomes: mono-> di-> tri-n-butyl amine. These results are discussed from the point of view of solvation as an important role in the determination of the relative strengths of butylamines, as well as the extent to which dinitrophenols are affected by chelation between the phenolic OH and ortho-nitro group. However, in chlorobenzene and ethyl acetate as solvents, the relative basic strengths of pyridine and aniline derivatives remain independent of the solvent when bromophenol blue is used as a reference acid. The of KBH+A- values for aniline derivatives proved to be more suitable for judging the effect of the substituent than the basic strength in aqueous solution

Mathematica as an Efficient Tool to Optimize the Kinetic Study of Ethyl Acetate Hydrolysis

Mathematica is a powerful program for computing both numeric and algebraic calculations as well as graphing two- and three-dimensional curves and surfaces. It is used increasingly in many fields of science now such as physics, engineering, chemistry and even biology because of the fast interaction of mathematics with almost the fields of science nowadays. We report here, optimizing the kinetic data for the hydrolysis of ethyl acetate through caustic soda via using Mathematica