مطالب

Mathematical models have the potential to provide a cost-effective, objective, and flexible approach to assessing management decisions, particularly when these decisions are strategic alternatives. In some instances, mathematical model is the only means available for evaluating and testing alternatives. However, in order for this potential to be realized, models must be valid for the application and must provide results that are credible and reliable. The process of ensuring validity, credibility, and reliability typically consists of three elements: verification, validation, and calibration. Model verification, validation and calibration are essential tasks for the development of the models that can be used to make predictions with quantified confidence. Quantifying the confidence and predictive accuracy of model provides the decision-maker with the information necessary for making high-consequence decisions. There appears to be little uniformity in the definition of each of these three process elements. There also appears to be a lack of consensus among model developers and model users, regarding the actions required to carry out each process element and the division of responsibilities between the two groups. This paper attempts to provide mathematical model developers and users with a framework for verification, validation and calibration of these models. Furthermore, each process element is clearly defined as is the role of model developers and model users. In view of the increasingly important role that models play in the evaluation of alternatives, and in view of the significant levels of effort required to conduct these evaluations, it is important that a systematic procedure for the verification, validation and calibration of mathematical models be clearly defined and understood by both model developers and model users.

This research develops a two-level model based on hypotheses, which concern relationships among role ambiguity, role conflict, job involvement and salesperson performance at individual level and collective sale self efficacy, customer orientation and competitive climate at sale unit level in Iranian food industry. Data was drawn from 482 sales people in 30 companies , using a 51-item self-reported questionnaire. Research model was tested in disaggregation, aggregation and multilevel approaches. The results from three approaches were different. Multilevel modeling analysis revealed that role ambiguity and role conflict have negative effects, but collective sale self efficacy and job involvement have positive effects on sales person performance. Results also showed that collective sale self efficacy has positive moderation effect on the relationship between job involvement and sales person performance. Collective sale self efficacy indicated positive moderation effect on the relationship between job involvement and sales person performance and negative moderation effect on the relationship between role conflict and sales person performance.

In this paper, we address the question that does FDI alone affect economic growth or interaction of FDI and human capital is required to boost economic growth. We develop the model with an expanding variety of products. We estimate the model using some advanced tests utilizing data on FDI flows from developed countries. We find stronger complementary effects between FDI and human capital on the productivity growth rate instead of having them as separate variables. This result is consistent with the idea that the flow of advanced technology brought along by FDI can increase the growth rate of the host economy only by interacting with that country's absorptive capability. JEL Classification: F21: O49

This paper aimed at probing the implementation of portfolio assessment in the writing classroom in an attempt to examine its effect(s) on EFL learners’ metadiscourse awareness. It addressed the following questions: Does portfolio assessment as a teaching technique have positive wash back effect on the participants’ achievement in their writing ability in an academic context? And to what extent do the students develop metadiscourse awareness in their writing by the treatment of portfolio assessment? The participants were the students of English literature enrolled for their composition course. After being homogenized for their proficiency level, they were randomly divided into an experimental group (EG) and a control group (CG). As the treatment, portfolio assessment was employed as the teaching technique for the experimental group. Data was then subjected to different statistical procedures. The results of data analysis revealed that the participants in the EG outperformed those in the CG with regard to the achievement in their overall writing ability. Second, based on chi-square results, participants in the EG used metadiscourse markers more correctly and efficiently compared with those in the CG. The results of the present study may have some implications for teaching of writing to EFL learners.

With day-increasing emphasis on communication as the chief objective of second language learning, willingness to communicate (hereafter WTC) has come into focus by many researchers, teachers, and foreign language institutes. Previous studies show that WTC is highly correlated with the two variables of perceived competence and communication apprehension. This study aimed to investigate the difference in WTC between male and female English major students at Khorasgan University, Iran. Firstly, 55 English major students were asked to respond to three questionnaires on WTC, perceived competence and communication apprehension. The data was analyzed using independent sample t-test. The results showed no significant difference between male and female students in WTC, perceived competence and communication apprehension. The results related to the effect of language proficiency on WTC, perceived competence, and communication apprehensions were also analyzed using one way ANOVA. The results showed no significant differences between the three different groups of students with different levels of language proficiency in their WTC, perceived competence, and communication apprehension