The accuracy of four approximations to noncentralF

The accuracy of the two-moment, three-moment, square root, and cube root approximations to the noncentralF distribution was assessed using 7,920 entries from Tiku’s (1967) power tables. Tiku’s tables list exact values of β for α= .005?.05, ν₁ = 1?12, ν₂ = 2?120, and ?= 0.5?3.0. Analysis of the errors showed generally satisfactory performance for all four approximations. The three-moment approximation was most accurate, registering a maximum error of only .009. The other three approximations had maximum errors of ±.02, except for the square root approximation at ν₂ = 2, where maximum errors of .05 occur. Approximation error increased with decreases in ν₁ and, less consistently, with increases in ν2. Error was nonmonotonically related to ?. A second investigation explored the accuracy of the approximations at values of αranging from .10 to .90. All four approximations degraded substantially in this situation, with maximum errors ranging from ?.09 to .05. If the analysis is restricted to cases where ν₁ τ; 1 and ν₂ τ; 2, maximum errors drop to roughly ±.03. We conclude that the approximations perform reasonably well for small αand moderately well for larger values, if certain restrictions are imposed. From a computational standpoint, however, there is little advantage to using approximate as opposed to exact methods unless exact values ofF _α are known in advance.     

Factors facilitating adjustment to unemployment: Implications for intervention

Conducted a community survey in the Fall of 1984 in a sample of high unemployment blue-collar census tracts in southeastern Michigan. Results of earlier analyses using these data showed that involuntarily unemployed workers had significantly elevated levels of depression, anxiety, somatization, and self-reported physical illness relative to a stably employed comparison group (Kessler, House, & Turner, 1987). Results presented in this paper document that this relationship is modified by social support (as measured by social integration and the availability of a confidant), self-concept, and various coping processes. Further analyses allowed us to determine the way in which these modifiers operate. The modifying effects of social support and coping operate primarily by buffering the impact of unemployment-related financial strain on the health outcomes. Self-concept operates primarily by attenuating vulnerability to other stressful life events. The implications of these results for the design and implementation of preventive interventions are discussed.     

Effects of prior juror experience on jury sentencing

The effect of prior juror service on jury sentencing was investigated in an archival study of 143 criminal trials resulting in convictions. Trials took place over two calendar years in a state circuit court requiring jurors to serve 30-day terms. Jurors sentenced defendants in each case according to a set of guidelines determined by trial judges. The severity of the sentences imposed by jurors was rated by 101 subjects on a scale of 1 (least severe) to 100 (most severe). The results indicated that the more experienced juries gave significantly more severe sentences than did the less experienced juries. This finding was unchanged when civil court experience was considered in addition to criminal court experience. Possible interpretations of these results are discussed.     

Mitigating Burnout Among High-NA Employees in Health Care: What Can Organizations Do?

The purpose of this study was to examine the extent to which factors in the nursing environment have differential effects on burnout levels among nurses high and low in negative affectivity (NA). Specifically, this field study examined the moderating relationships among role ambiguity, role conflict, and collective efficacy on the NA–burnout relationship among nurses in a hospital setting. Findings suggest that perceived role conflict exacerbates while perceptions of collective efficacy reduce specific dimensions of burnout for nurses high in NA. These results offer some evidence regarding which environmental characteristics may mitigate burnout for high-NA nurses.     

Iterated Belief Revision, Reliability, and Inductive Amnesia

Belief revision theory concerns methods for reformulating an agent's epistemic state when the agent's beliefs are refuted by new information. The usual guiding principle in the design of such methods is to preserve as much of the agent's epistemic state as possible when the state is revised. Learning theoretic research focuses, instead, on a learning method's reliability or ability to converge to true, informative beliefs over a wide range of possible environments. This paper bridges the two perspectives by assessing the reliability of several proposed belief revision operators. Stringent conceptions of minimal change are shown to occasion a limitation called inductive amnesia: they can predict the future only if they cannot remember the past. Avoidance of inductive amnesia can therefore function as a plausible and hitherto unrecognized constraint on the design of belief revision operators.     

VSearch: Macintosh software for experiments in visual search

In this paper, we describe software that turns a Macintosh computer into an off-the-shelf tool for experiments on visual search. Our design goals included portability (between members of the Macintosh computer family and between various research settings), user-friendliness (equivalent to Macintosh programming standards), flexibility (to allow replication and extension of important experiments on visual search), and adaptability (very short design-to-data and data-to-analysis turnaround times). We describe how the software meets these goals in three major phases of an experiment: stimulus construction, experimental control, and statistical analysis. We then list several landmark studies of visual search that can be easily designed and extended with the software. Finally, we outline plans for expanding the experimental variations that will be supported in future versions of the software.     

Physicians,entrepreneurism and the problem of conflict of interest

This paper examines the ethical issues of conflict of interest raised by the burgeoning development of physician involvement in for-profit entrepreneurial activities outside their practice. After documenting the nature and extent of these activities, and their potential for conflicts of interest, the paper assesses the major arguments for and against physicians' referral of patients to facilities they own or in which they invest. The paper concludes that an outright ban on such activity seems ethically warranted.     

An MMPI-based empirical model of malingering and deception

The empirically-based model of malingering and deception described by Rogers (1984b) was operationalized using MMPI and clinical interview data. Subjects (N = 159) were patients committed to an inpatient forensic hospital as ‘Incompetent to Stand Trial’ or ‘Not Guilty by Reason of Insanity’. Inter-rater reliability was acceptable for the 11 criteria used to define response styles. Each subject was categorized into one of five response style groups: ‘Reliable’, ‘Malingering’, ‘Defensive’, ‘Irrelevant’, or ‘Unclassifiable’. Factor analysis of the rating criteria yielded four factors, three of which are comparable to the assigned groups, providing some validation for the constructs underlying these groups.