Until recently the design of experiments in the behavioral and social sciences that focused on interaction effects demanded the use of the parametric analysis of variance. Yet, researchers have been concerned by the presence of nonnormally distributed variables. Although nonparametric statistics are recommended in these situations, researchers often rely on the robustness of parametric tests. Further, often it is assumed that nonparametric methods lack statistical power and that there is a paucity of techniques in more complicated research designs, such as in testing for interaction effects. This paper reviewed (a) research in the past decade and a half that addressed concerns in selecting parametric and nonparametric statistics and (b) 10 recently developed nonparametric techniques for the testing of interactions in experimental design. The review shows that these new techniques are robust, powerful, versatile, and easy to compute. An application of selected nonparametric techniques on fabricated data is...

Statistics for Applied Economics and Business

Nonparametric Tests of Interaction in Experimental Design

There has long been a concern over the volatility of exchange-rates and their impact on the volume of foreign trade.' However, very little attention has been paid to the choice of an appropriate volatility variable as well as the proper specification of the trade equation. The sample standard deviation of the exchange rate has been used as a proxy for exchangerate uncertainty in empirical studies that examine the effects of exchange-rate uncertainty on the volume of foreign trade. See, for example, Akhtar and Hilton [1] and Gotur [27]. These studies have provided conflicting evidence on this issue. It has been argued that use of the sample standard deviation is inappropriate because the empirical distribution of exchange rates is not normal [22; 10]. In this regard, subsequent empirical research [12; 36; 40; 41; 11] has employed a moving standard deviation of the rate of change of the exchange rate as a proxy for exchange-rate uncertainty. Chowdhury [11] obtained a clear pattern of results that support the hypothesis that the higher volatility of exchange rates led to a reduction in international trade transactions after the breakdown of the Bretton Woods system in March 1973. Other studies have reported ambiguous results.2 The moving standard deviation used in these studies has been criticized in the literature for (a) ignoring relevant information on the random process generating exchange rates [18]; (b) underestimating the effect of volatility on decisions [52]; (c) distorting the measurement of the volatility variable by smoothing the series [9]; and (d) injecting "an element of arbitrariness into the calculation" through decisions about the order (m) of the moving average [43].3

background

Conditional Exchange-Rate Volatility and the Volume of Foreign Trade: Evidence from Seven Industrialized Countries*

Ever since MYCIN introduced the idea of computer-based explanations to the artificial intelligence community, it has come to be taken for granted that all knowledge-based systems (KBS) need to provide explanations.
The first part of this dissertation proposes a cognitive learning theory based model that both clarifies the reasons as to why KBS need to provide explanations and serves as the basis for conceptualizing the provision of KBS explanations. Using the concepts of the feedforward and feedback operators of cognitive learning it develops strategies for providing KBS explanations and uses them to classify the various types of explanations found in current KBS applications. The roles of feedforward and feedback explanations within the context of the theory of cognitive skill acquisition and a model of expert judgment are also analyzed. These, together with past studies of KBS explanations, suggest that user expertise, the types of explanations provided, and the level of user agreement are significant factors that influence the explanation seeking behavior of users. The dissertation also explores the effects of the use of KBS explanations in judgmental decision making situations supported by a KBS. It identifies and considers four distinct categories of potential effects of the use of explanations--learning effects, perceived effects, behavioral effects, and effects on judgmental decision making.
The second part of the dissertation empirically evaluates the explanation provision strategies in a laboratory experiment in which 80 novice and expert subjects used a KBS for financial analysis to make judgments under conditions of uncertainty. The experiment was designed specifically to investigate the following fundamental research questions: (1) To what extent are the various kinds of explanations used? (2) How does user expertise, the feedforward and feedback provision of explanations, and the level of user agreement influence the amount and the types of explanations that are used? and (3) Does the use of explanations affect the accuracy of judgmental decision-making and user perceptions of usefulness?
Some of the major results relating to the determinants of the use of KBS explanations include: (1) user expertise is not a determinant of the proportion of explanations used but influences the types of explanations that are used, (2) explanation provision strategy is a critical determinant of the use of KBS explanations with feedback explanations being used significantly more than feedforward explanations, and (3) the three types of explanations are used in different proportions with the Why and How explanations being used significantly more that the Strategic explanations. (Abstract shortened by UMI.)

Additional excerpts

An experimental investigation of the use of explanations provided by knowledge-based systems

Guidelines for the use of protected/permissive left-turn signal phasing were developed by collecting and analyzing data on traffic and roadway conditions for protected-only, protected/permissive, and permissive left-turn phasings to identify relationships among these conditions and signal phasings. The following left-turn signal aspects are addressed: (a) traffic volume based on the peak-hour minimum left-turn volume and the product of the peak-hour left-turn and opposing volumes with lower and upper limits, (b) annual left-turn accident experience based on the critical number and rate, (c) left-turn traffic conflict experience based on the critical number and rate, (d) left-turn delay, (e) site condition, (f) user cost savings for protected/permissive versus protected-only left-turn phasing, and (g) traffic engineering judgment.

Guidelines for protected/permissive left-turn signal phasing

In most African countries, banana production has been consigned to subsistence production. However, a few countries, especially in Francophone West Africa, have recognised the commercial importance of banana, and have used their special relationship with France to export bananas. This has led to the dualization of the banana sector, with the traditional system existing side by side with a modern sector geared towards export trade. This book is one of the few comprehensive studies that have incorporated both the agronomic and economic aspects of banana production and marketing in Africa. It looks at all facets of banana production, from an historical perspective to the various traditional and modern technologies involved. The marketing aspect covers both the domestic and international trade, with emphasis on the preferential (ACP / DOM Lome Convention) and the open markets of the European Union. The book is a major contribution to understanding the internationalisation of the banana trade and to its ever-increasing investment portfolio, as the backbone of many a developing tropical economy. Although the emphasis is placed on Cameroon, other relevant African, tropical and subtropical banana-producing countries are mentioned where necessary, especially in the export sector where a degree of competition existed. Further, agricultural practices, soils, meteorological and climatological characteristics, pests and diseases, personnel and banana varieties grown, mean that findings in Cameroon are of relevance to other banana-producing countries, especially in Africa. Meanwhile, other African and tropical countries still contemplating entry into banana exports would benefit from the Cameroon experience. The book is of especial relevance to agronomists, entomologists, economists, farm managers, government policy makers, large, medium and small scale banana growers, and students and teachers in universities and schools of agriculture.

Statistics for Applied Economics and Business

Citations

Nonparametric Tests of Interaction in Experimental Design

Conditional Exchange-Rate Volatility and the Volume of Foreign Trade: Evidence from Seven Industrialized Countries*

An experimental investigation of the use of explanations provided by knowledge-based systems

Guidelines for protected/permissive left-turn signal phasing

Economics of Banana Production and Marketing in the Tropics

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