A Step-by-Step Guide to Propensity Score Matching in R

Propensity score matching is a statistical technique in which a treatment case is matched with one or more control cases based on each case’s propensity score. This matching can help strengthen causal arguments in quasi-experimental and observational studies by reducing selection bias. In this article we concentrate on how to conduct propensity score matching using an example from the field of education. Our goal is to provide information that will bring propensity score matching within the reach of research and evaluation practitioners. Accessed 57,198 times on https://pareonline.net from November 19, 2014 to December 31, 2019. For downloads from January 1, 2020 forward, please click on the PlumX Metrics link to the right

Spredte undersøgelser om toldbyrden paa landbrugets forbrug.

Spredte undersøgelser om toldbyrden paa landbrugets forbrug

Proposing new variables for the identification of strategic groups in franchising

The identification of strategic groups in the Spanish franchising area is the main aim of this study. The authors have added some new strategic variables (not used before) to the study and have classified franchisors between sectors and distribution strategy. The results reveal the existence of four perfectly differentiated strategic groups (types of franchisors). One of the major implications of this study is that the variables that build a strategic group vary depending on the respective sector the network operates in and its distribution strategy. This fact indicates that including sector and distribution strategy is absolutely necessary to achieve good classifications of franchisor type

A Methodological Review of the Articles Publishes in Georgia Educational Researcher from 2003-2010

Methodological reviews, reviews that concentrate on research methods rather than research outcomes, have been used in a variety of fields to improve research practice, inform debate, and identify islands of practice. In this article, we report on the results of a methodological review of all of the articles published in Georgia Educational Researcher from 2003-2010. We examined the methodological characteristics, authorial characteristics, and methodological quality of those articles using quantitative content analysis. The major findings were that (a) the proportions of the type and traditions of articles published in Georgia Educational Researcher were similar to the proportions in education research articles in general, (b) case study research and correlational research were most prominent, (c) a few universities accounted for most of the articles published, (d) male and female authors’ articles were published in equitable proportions, and (e) there were no statistically significant differences in methodological quality between genders, university affiliations, types of research, or years of publication. We end with a few suggestions for improving the quality of qualitative research articles in the Georgia Educational Researcher

Franchise Business Development Model: Theoretical Considerations

Franchising is not a popular business development form in Lithuania. Only 0.02% of all Lithuanian companies use franchising for business development, while in most of the developed countries franchise is recognized as a convenient business expansion form. So, what factors determine such differences in the use of franchising? Analysis of related literature showed, that mainly researchers analyse some aspects of franchising, however there is no systematized analysis which covers all the main franchise development elements. Therefore, the aim of this article is to systematize franchise business development phases, main elements and factors, influencing this process and to propose a theoretical franchise system development model. Thus, theoretical considerations about the main phases and elements of franchise system development as well as advantages and disadvantages of the system are analysed in the article. These theoretical considerations are generalized in theoretical franchise system development model, which shows, that development of franchise business consists of particular steps, starting from favourable conditions for the system to emerge; intention and ability of franchisor to form franchise based on his business; the establishment and initial development of franchise system; and its further functioning. The article does not test the model and even does not discuss the operationalization of it. Operationalization of the model as well as empirical evidence is presented by the authors in the forthcoming articles

Micellar structure and transformations in sodium alkylbenzenesulfonate (NaLAS) aqueous solutions: effects of concentration, temperature, and salt

We investigate the shape, dimensions, and transformation pathways of micelles of linear sodium alkylbenzenesulfonate (NaLAS), a common anionic surfactant, in aqueous solution. Employing Small Angle Neutron Scattering (SANS) and surface tensiometry, we quantify the effects of surfactant concentration (0.6–15 wt%), temperature (5–40 °C) and added salt (≤0.35 M Na2SO4). Spherical micelles form at low NaLAS (≤2.6 wt%) concentration in water, and become elongated with increasing concentration and decreasing temperature. Addition of salt reduces the critical micelle concentration (CMC) and thus promotes the formation of micelles. At fixed NaLAS concentration, salt addition causes spherical micelles to grow into cylindrical micelles, and then multilamellar vesicles (MLVs), which we examine by SANS and cryo-TEM. Above a threshold salt concentration, the MLVs reach diameters of 100 s of nm to few μm, eventually causing precipitation. While the salt concentrations associated with the micelle-to-cylinder transformation increase only slightly with temperature, those required for the cylinder-to-MLV transformation exhibit a pronounced, linear temperature dependence, which we examine in detail. Our study establishes a solution structure map for this model anionic surfactant in water, quantifying the combined roles of concentration, temperature and salt, at practically relevant conditions

Removal of Tannic Acid From Aqueous Solution by Cloud Point Extraction and Investigation of Surfactant Regeneration by Microemulsion Extraction

The aim of this work is the extraction of tannic acid (TA) with two commercial nonionic surfactants, separately: Lutensol ON 30 and Triton X-114 (TX-114).The experimental cloud point extraction results are expressed by four responses to surfactant concentration and temperature variations: extent of TA extraction (E), remaining solute (X s,w) and surfactant (X t,w) concentrations in dilute phase and volume fraction of coacervate (Φc) at equilibrium. An empirical smoothing method was used and the results are represented on three dimensional plots. In optimal conditions, the extraction extent of TA reaches 95 and 87 % using TX-114 and Lutensol ON 30, respectively. Sodium sulfate, cetyltrimethylammonium bromide (CTAB) addition and pH effect are also studied. Finally, the possibility of recycling of the surfactant is proved