Portfolio analysis in practice

Much has been written about the theory of portfolio management and the consultant's approach to its use. This article describes a practical example of the implementation of the technique by a management without the assistance of external consultants. It shows how the technique was adapted and extended to meet the needs of the company. It further describes how the practical problems encountered during implementation led to the development of a system that provided strategically important data both for staff and operating management in a relatively digestible format.     

Robustness of the linear discriminant function to nonnormality: Johnson's system

The asymptotic distribution of the Errors of Misclassification in using the Linear Discriminant Function is investigated here. The purpose is to study the effects of nonnormality on these errors. The class of distributions considered is the Johnson's system. Each of the three random variables can be transformed to normality. In one particular case numerical evaluations are made, based on which it is possible to recommend whether or not it is necessary to make the transformation prior to classification. In a parallel study, we present similar results for the Edgeworth Series distribution, where the random variables cannot be transformed to normality.     

The benefits of a nap during prolonged work and wakefulness

Prolonged work scenarios with demands for sustained performance are increasingly common. Because sleep loss inevitably compromises functioning in such situations, napping has been proposed as a countermeasure. The optimal timing of the nap relative to its benefits for performance and mood is not known, however. To address this issue, 41 healthy adults were permitted a two-hour nap at one of five times during a 56-hour period of intermittent work, with no other sleep. Naps were placed 12 hours apart, near the circadian peak (P) or trough (T), and were preceded by 6(P), 18(T), 30(P), 42(T), or 54(P) hours of wakefulness. Work test bouts occurred every few hours and consisted of a variety of psychomotor and cognitive tasks as well as mood scales completed at the beginning, middle and end of each bout. A total of eight performance and 24 mood parameters were derived from the bouts and compared between groups at all test points prior to and following the naps. An estimate of the extent to which each nap condition differed from the control (P54) condition was derived by totalling the proportion of test points that yielded statistically significant results relative to the total number of tests conducted both before and after naps.

Although all performance and most mood parameters displayed a circadian-modulated deterioration as the protocol progressed, a nap appeared to attentuate the extent of this change in all performance parameters but not in mood parameters. Overall, the timing of the nap across days and within the circadian cycle was irrelevant to its effect on performance, suggesting that it diminished the intrusion of sleepiness into behavioural functioning, even though subjects were phenomenally unaware of this benefit.     

A microcomputer simulation of an automated non ferrous sand casting foundry

In this paper the authors describe the simulation of an automated non ferrous sand casting foundry using a popular microcomputer to evaluate the effects on output of several machine loading rules. The programmed facilities allow the scheduler to experiment with his own loading rules on actual, rather than hypothetical, batches of jobs which, if found to increase output or some other measure of performance, can be stored for scheduling future jobs. Scheduling in such an interactive manner allows the simulation program to learn and improve upon scheduling rules on actual jobs in much the same way as the human scheduler would in practice, without the associated risks of affecting production.     

Power: A Conceptual Framework*

Symbolic interactionism lacks a coherent conception of power. This paper defines power in a manner consistent with the interactionist perspective. Power is conceptualized as a collective transaction characterized by a division of labor, movement toward a common end, and flexible coordination between opponents. Power is distinguished from other types of collective transactions by asymmetrical interaction, a conflict of interests between opponents, and the intentional production of compliance. Some implications of considering power as a collective transaction are then examined.     

Family Therapy Process in a Family Therapy Seminar

The interaction between leaders and members in a year-long family therapy seminar is systematically compared to the process that unfolds between therapist and family during the course of family therapy. A five stage developmental process common to both is postulated and described: (1) Battle for Structure, (2) Naive Enthusiasm, (3) Conflictual Frustration, (4) Task Orientation, and (5) Mutuality. The dynamic elements of each stage are analyzed and factors affecting their development are identified. It is concluded that this five stage process occurs in all similar groups, but that the content of each stage may vary widely from group to group.     

Some computational problems related to multinomial trials

Efficient numerical algorithms are developed to evaluate several probabilities related to multinomial trials.In the first part of the paper, the probability distribution of the number of trials until the alternatives j, j = 1,… m, have occurred at least i_j times is computed. The multinomial trials involve the m alternatives l,…, m, with positive probabilities P_l-P_m of occurrence. In the second part, several aspects of a multinomial subset selection problem, discussed by S. S. Gupta and K. Nagel, are investigated.