Robustness estimators of location:a classification of linear and adaptive estimators

Real-world data sets may be described in terms similar to trauma cases- 'messy' with 'high morbidity'. Alternative estimators to the traditional mean are examined via a simulation study over a wide range of both symmetric and asymmetric distributions. These alternative estimators are data depenmdent and, in most cases, represent data far better than the usual mean. Princeton and post-Princeton linear and adaptive estimators of location are summarized, and a classification scheme based on an ancillary or selector statistic is proposed. The computational formulae for the collection of estimators have been standardized, as have the ancillary statistics. We classify these estimators by their computational form, give the computational formulae for each in a standardized notation, evaluate the subclass of estimators, and identify our 'winner' in that class.     

Contributions to two-sample statistics

When testing the equality of the means from two independent normally distributed populations given that the variances of the two populations are unknown but assumed equal, the classical Student's two-sample t-test is recommended. If the underlying population distributions are normal with unequal and unknown variances, either Welch's t-statistic or Satterthwaite's approximate F test is suggested. However, Welch's procedure is non-robust under most non-normal distributions. There is a variable tolerance level around the strict assumptions of data independence, homogeneity of variances, and identical and normal distributions. Few textbooks offer alternatives when one or more of the underlying assumptions are not defensible. While there are more than a few non-parametric (rank) procedures that provide alternatives to Student's t-test, we restrict this review to the promising alternatives to Student's two-sample t-test in non-normal models.     

How right-to-work laws affect wages

I examine the wage effects of Right-To-Work (RTW). Using state-level data, I estimate that, ceteris paribus, RTW states have average wages that are significantly higher than non-RTW states. This result is robust is across a wide variety of specifications. An important distinctive of this study is that it controls for state economic conditions at the time states adopted RTW. States that adopted RTW were generally poorer than other states. Failure to control for these initial conditions may be the reason that previous studies have not identified a positive wage impact for RTW. I thank Kevin Grier for valuable comments and Lawrence Mishel of the Economie Policy Institute for constructive criticisms on an earlier version of this research.     

Drinking plans and drinking outcomes: examining young adults' weekend drinking behavior

This study examined relationships among drinking intentions, environments, and outcomes in a random sample of 566 undergraduate college students. Telephone interviews were conducted with respondents before and after a single weekend assessing drinking intentions for the coming weekend related to subsequent drinking behaviors. Latent class analyses found evidence for four distinct drinking environments distinguished by private/public setting and presence of few/many intoxicated people. There was evidence that the drinking environment mediated the relationship between drinking intentions and heavy episodic drinking in this young adult sample. Future research might focus on examining person/environment interactions as they relate to heavy episodic drinking.     

Risk, uncertainty and family formation: The social context of poverty groups

Abstract Despite the assumptions of many demographers that the net returns from children for non-elite groups in underdeveloped areas are likely to be negative, high fertility persists in most of these societies. Both cultural and institutional explanations have been proposed to account for this. We attempt to provide some mediation between these competing models, by introducing the elements of risk and uncertainty as factors likely to induce poverty and lead works to opt for the 'high fertility, low quality' pattern of investment of time and money in family formation. Drawing upon the work of Wharton in subsistence agriculture practices, several alternative decision-making models are proposed to account for both the persistence of high fertility, and the declines that have been registered in selected areas, such as Taiwan and perhaps China. The empirical work of Mueller on Taiwanese expectations of returns on children and the concomitant variation in family-size preferences is consistent with the models proposed. Some implications for uncertainty and risk-reduction strategies in family planning and other social welfare programmes are drawn.     

Brownian–Laplace Motion and Its Use in Financial Modelling

Brownian-Laplace motion is a Lévy process which has both continuous (Brownian) and discontinuous (Laplace motion) components. The increments of the process follow a generalized normal Laplace (GNL) distribution which exhibits positive kurtosis and can be either symmetrical or exhibit skewness. The degree of kurtosis in the increments increases as the time between observations decreases. This and other properties render Brownian-Laplace motion a good candidate model for the motion of logarithmic stock prices. An option pricing formula for European call options is derived and it is used to calculate numerically the value of such an option both using nominal parameter values (to explore its dependence upon them) and those obtained as estimates from real stock price data.     

Examining the Effects of Feedback Accuracy and Timing on Skill Acquisition

ABSTRACT

Feedback involves providing information about past performance and indicating how to improve future performance. Although the literature contains numerous examples of feedback as an effective method for improving performance across a range of organizational settings, much remains unknown about the specifics of how feedback acts to change behavior. This study evaluated the combined effects of feedback accuracy (100%, 80%, 20%) and timing (feedback following each trial or after a block of 25 trials) on skill acquisition in undergraduate students when presented with a computerized match-to-sample task that required participants to learn the names of shapes. Results reveal that feedback accuracy had a significantly greater effect on performance than the timing of the feedback.