A Reexamination of Card and Krueger's State-Level Study of the Minimum Wage

Card and Krueger's (1995) difference-in-difference study of the 1990-1991 federal minimum wage hikes compared states by the proportion of workers directly affected by the minimum wage. They found "no evidence that the increase in the minimum wage significantly lowered teenage employment rates more in highly affected states" and they concluded the minimum wage did not reduce employment. Their paper was highly influential and convinced many that the minimum wage did not reduce employment. However, when I apply their model to the 1996-1997 federal minimum wage hike, I find that increases in the minimum wage significantly lowered teenage employment rates more in highly affected states. Using Card and Krueger's interpretation, this implies the minimum wage did reduce teenage employment.     

The Experience-Earnings Profile: Productivity-Augmenting or Purely Contractual? Evidence from the UK

We test the human capital interpretation of the experience-earnings profile. Does the upward sloping portion of the experience-earnings profile reflect on-the-job training which in turn causes the experience-productivity profile to slope upwards, or do purely contractual factors determine the nature of life-cycle earnings. Herein, we provide additional evidence on the relationship between productivity and earnings by examining earnings differentials in the UK academic labor market for economists. Using a test first suggested by Mincer, we find that the empirical results are consistent with human capital theory. We find that, although the positive relationship between earnings and experience persists when individual productivity measures are included in the salary equations for lecturers and senior lecturers, the positive relationship becomes statistically insignificant when the same productivity measures are included in the salary equations for professors. For lecturers and senior lecturers, the experience-salary profile properly reflects the structure of the national pay scale rather than variations in individual research productivity. At the professor level, where individual salaries are not determined by a pay scale, the data support the human capital explanation of the positive experience-earnings profile.

Camera-Related Behaviors during Video Recorded Medical Interactions

Video recording provides an objective record of the content of medical interactions. However, there is concern that cameras may be reactive measurement devices that alter what normally transpires during interactions. This study addressed potential reactivity of cameras in medical interactions. Interactions between 45 patients and 14 medical oncologists were video recorded and coded for camera-related behaviors. Eleven of 45 patients performed none of the behaviors. Among the other patients, camera-related behaviors were infrequent and, on average, constituted about 0.1% (one-tenth of one percent) of total interaction time. Behaviors occurred most often in very early stages of interactions, and when physicians were absent from the room. Seven physicians showed camera-related behaviors, comprising less than 0.1% of the time they were in the interaction. Results suggest video recording can provide nonreactive means of studying medical interactions.

Multivariate process dispersion monitoring without subgrouping

The memory-type adaptive and non-adaptive control charts are among the best control charts for detecting small-to-moderate changes in the process parameter(s). In this paper, we propose the Crosier CUSUM (CCUSUM), EWMA, adaptive CCUSUM (ACCUSUM) and adaptive EWMA (AEWMA) charts for efficiently monitoring the changes in the covariance matrix of a multivariate normal process without subgrouping. Using extensive Monte Carlo simulations, the length characteristics of these control charts are computed. It turns out that the ACCUSUM and AEWMA charts perform uniformly and substantially better than the CCUSUM and EWMA charts when detecting a range of shift sizes in the covariance matrix. Moreover, the AEWMA chart outperforms the ACCUSUM chart. A real dataset is used to explain the implementation of the proposed control charts.     

AN EMPIRICAL ASSESSMENT OF COMPUTER-ASSISTED DECISION ANALYSIS*

Decision analysis tools often are used in semistructured and ill-structured situations. While some researchers have argued that computerized decision analysis programs may improve decision quality in such situations, research support for this assertion is weak. In this laboratory study, business students used a computerized decision-analysis program with short strategic-management cases to prepare decision reports. Independent raters' perceptions of aided and unaided decision performance were contrasted, attitudes of students toward the program were assessed, individual differences were correlated with attitudes, and the program's impact on students' perceptions of their decision processes and performance was examined. Student attitudes toward the computerized aid were favorable, and individual differences in reactions generally were as predicted. However, the program did not improve the independent ratings of students' decision reports and recommendations. These findings suggest that computerized decision aids should be adopted cautiously. If such aids result in positive user affect and heightened decision confidence without corresponding improvements in decision quality, they may be dysfunctional. Rigorous research methodologies which incorporate independent evaluations of analyses and decisions are recommended for use in future research on computerized decision-analysis programs.