NEW EVIDENCE ON NATIONAL BOARD CERTIFICATION AS A SIGNAL OF TEACHER QUALITY

Using longitudinal data from North Carolina that contains detailed identifiers, we estimate the effect of having a National Board for Professional Teaching Standards (NBPTS) teacher on academic achievement. We identify the effects of an NBPTS teacher exploiting multiple sources of variation including traditional‐lagged achievement models, twin‐ and sibling‐fixed effects, and aggregate grade‐level variation. Our preferred estimates show that students taught by National Board certified teachers have higher math and reading scores by 0.04 and 0.01 of a standard deviation. We find that an NBPTS math teacher increases the present value of students' lifetime income by $48,000. (JEL I20, I21, J2444)     

A conceptual model for the process of IT innovation adoption in organizations

In this paper, we develop a conceptual model for IT innovation adoption process in organizations. The model utilizes Diffusion of Innovation (DOI) theory, Theory of Reasoned Action (TRA), Technology Acceptance Model (TAM), Theory of Planned Behaviour (TPB) and a framework that contains characteristics of innovation, organization, environment, chief executive officer (CEO) and user acceptance. The model presents IT adoption as a sequence of stages, progressing from initiation to adoption-decision to implementation. The study presents a model with an interactive process perspective which considers organizational level analysis until acquisition of technology and individual level analysis for the user acceptance of IT.     

Detecting structural change with heteroskedasticity

The hypothesis of structural stability that the regression coefficients do not change over time is central to all applications of linear regression models. It is rather surprising that existing theory as well as practice focus on testing for structural change under homoskedasticity – that is, regression coefficients may change, but the variances remain the same. Since structural change can, and often does, involve changes in variances, this is a puzzling gap in the literature. Our main focus in this paper is to utilize a newly developed test (MZ) by Maasoumi et al. (2010 Maasoumi, E., Zaman, A., Ahmed, M. (2010). Tests for structural change, aggregation, and homogeneity. Econ Model. 27(6):1382–1391.[Crossref], [Web of Science ®] , [Google Scholar]) that tests simultaneously for break in regression coefficients as well as in variance. Currently, the sup F test is most widely used for structural change. This has certain optimality properties shown by Andrews (1993 Andrews, D.W.K. (1993). Test for parameter instability and structural change with unknown change point. Econometrica. 61(4):821–856.[Crossref], [Web of Science ®] , [Google Scholar]). However, this test assumes homoskedasticity across the structural change. We introduce the sup MZ test which caters to unknown breakpoints, and also compare it to the sup F. Our Monte Carlo results show that sup MZ test incurs only a low cost in case of homoskedasticity while having hugely better performance in case of heteroskedasticity. The simulation results are further supported by providing a real-world application. In real-world datasets, we find that structural change often involves heteroskedasticity. In such cases, the sup F test can fail to detect structural breaks and give misleading results, while the sup MZ test works well. We conclude that the sup MZ test is superior to current methodology for detecting structural change.     

The Changing Transmission of Uncertainty Shocks in the U.S.

This article investigates if the impact of uncertainty shocks on the U.S. economy has changed over time. To this end, we develop an extended factor augmented vector autoregression (VAR) model that simultaneously allows the estimation of a measure of uncertainty and its time-varying impact on a range of variables. We find that the impact of uncertainty shocks on real activity and financial variables has declined systematically over time. In contrast, the response of inflation and the short-term interest rate to this shock has remained fairly stable. Simulations from a nonlinear dynamic stochastic general equilibrium (DSGE) model suggest that these empirical results are consistent with an increase in the monetary authorities’ antiinflation stance and a “flattening” of the Phillips curve. Supplementary materials for this article are available online.     

Testing for Additivity at Select Mixture Groups of Interest Based on Statistical Equivalence Testing Methods

Several assumptions, defined and undefined, are used in the toxicity assessment of chemical mixtures. In scientific practice mixture components in the low-dose region, particularly subthreshold doses, are often assumed to behave additively (i.e., zero interaction) based on heuristic arguments. This assumption has important implications in the practice of risk assessment, but has not been experimentally tested. We have developed methodology to test for additivity in the sense of Berenbaum (Advances in Cancer Research, 1981), based on the statistical equivalence testing literature where the null hypothesis of interaction is rejected for the alternative hypothesis of additivity when data support the claim. The implication of this approach is that conclusions of additivity are made with a false positive rate controlled by the experimenter. The claim of additivity is based on prespecified additivity margins, which are chosen using expert biological judgment such that small deviations from additivity, which are not considered to be biologically important, are not statistically significant. This approach is in contrast to the usual hypothesis-testing framework that assumes additivity in the null hypothesis and rejects when there is significant evidence of interaction. In this scenario, failure to reject may be due to lack of statistical power making the claim of additivity problematic. The proposed method is illustrated in a mixture of five organophosphorus pesticides that were experimentally evaluated alone and at relevant mixing ratios. Motor activity was assessed in adult male rats following acute exposure. Four low-dose mixture groups were evaluated. Evidence of additivity is found in three of the four low-dose mixture groups. The proposed method tests for additivity of the whole mixture and does not take into account subset interactions (e.g., synergistic, antagonistic) that may have occurred and cancelled each other out.     

Stochastic analysis of a complex system with an auxiliary unit

This paper considers the stochastic analysis of a complex system having three units. The first two units are designated as unit-1 and unit-2 while the third unit is called an auxiliary unit (unit-3) which enhances the range of transmission and efficiency of unit-1. Joint distributions of failure and repair times are bivariate exponential (B.V.E.) with different parameters. Regenerative point technique is used to obtain various reliability characteristics of the system under study. Behaviour of some characteristics has also been studied through graphs.     

EVOLVING INTERNATIONAL INFLATION DYNAMICS: WORLD AND COUNTRY‐SPECIFIC FACTORS

The decline in the level and persistence of inflation over the 1980s is a common feature of the most industrialized economies in the world. The rise in inflation volatility of the late 1970s and the subsequent fall of the 1980s is country specific for the UK, Canada, and, to a lesser extent, the United States, Italy, and Japan. Since the late 1980s, inflation predictability has declined significantly across the industrialized world. We link the empirical results to recent theories of international inflation.