Probing three-way interactions in moderated multiple regression:Development and application of a slope difference test

Researchers often use 3-way interactions in moderated multiple regression analysis to test the joint effect of 3 independent variables on a dependent variable. However, further probing of significant interaction terms varies considerably and is sometimes error prone. The authors developed a significance test for slope differences in 3-way interactions and illustrate its importance for testing psychological hypotheses. Monte Carlo simulations revealed that sample size, magnitude of the slope difference, and data reliability affected test power. Application of the test to published data yielded detection of some slope differences that were undetected by alternative probing techniques and led to changes of results and conclusions. The authors conclude by discussing the test's applicability for psychological research. Copyright 2006 by the American Psychological Association.

Data analysis methods in optometry: is there a difference between two samples? Part 2.

In this second article, statistical ideas are extended to the problem of testing whether there is a true difference between two samples of measurements. First, it will be shown that the difference between the means of two samples comes from a population of such differences which is normally distributed. Second, the 't' distribution, one of the most important in statistics, will be applied to a test of the difference between two means using a simple data set drawn from a clinical experiment in optometry. Third, in making a t-test, a statistical judgement is made as to whether there is a significant difference between the means of two samples. Before the widespread use of statistical software, this judgement was made with reference to a statistical table. Even if such tables are not used, it is useful to understand their logical structure and how to use them. Finally, the analysis of data, which are known to depart significantly from the normal distribution, will be described.

Direct observation of R...R distances in rare-earth (R) phosphate glasses by magnetic difference neutron diffraction

A magnetic difference neutron diffraction study of a rare-earth (Tb) phosphate glass has revealed exclusively the Tb...Tb distances. The difference between data taken with and without an applied magnetic field of 4 T shows Tb...Tb pairwise atomic correlations at 3.9 and 6.4 A, respectively, with relative coordination numbers of 1:14. The first distance arises when two Tb3+ ions share a common oxygen neighbor, and indicates a clustering of rare-earth ions. The second distance arises when two Tb3+ ions are coordinated to different oxygens in the same PO4 group, in a near-linear arrangement.

Making a difference:critical linguistic analysis in a legal context

One of the major problems for Critical Discourse Analysts is how to move on from their insightful critical analyses to successfully 'acting on the world in order to transform it'. This paper discusses, with detailed exemplification, some of the areas where linguists have moved beyond description to acting on and changing the world. Examples from three murder trials show how essential it is, in order to protect the rights of witnesses and defendants, to have audio records of significant interviews with police officers. The article moves on to discuss the potentially serious consequences of the many communicative problems inherent in legal/lay interaction and illustrates a few of the linguist-led improvements to important texts. Finally, the article turns to the problems of using linguistic data to try to determine the geographical origin of asylum seekers. The intention of the article is to act as a call to arms to linguists; it concludes with the observation that 'innumerable mountains remain for those with a critical linguistic perspective who would like to try to move one'. © 2011 John Benjamins Publishing Company.

Uncovering the root cause of ethnic difference in ability testing:differential test functioning, test familiarity and trait optimism as explanations of ethnic group differences

The present research represents a coherent approach to understanding the root causes of ethnic group differences in ability test performance. Two studies were conducted, each of which was designed to address a key knowledge gap in the ethnic bias literature. In Study 1, both the LR Method of Differential Item Functioning (DIF) detection and Mixture Latent Variable Modelling were used to investigate the degree to which Differential Test Functioning (DTF) could explain ethnic group test performance differences in a large, previously unpublished dataset. Though mean test score differences were observed between a number of ethnic groups, neither technique was able to identify ethnic DTF. This calls into question the practical application of DTF to understanding these group differences. Study 2 investigated whether a number of non-cognitive factors might explain ethnic group test performance differences on a variety of ability tests. Two factors – test familiarity and trait optimism – were able to explain a large proportion of ethnic group test score differences. Furthermore, test familiarity was found to mediate the relationship between socio-economic factors – particularly participant educational level and familial social status – and test performance, suggesting that test familiarity develops over time through the mechanism of exposure to ability testing in other contexts. These findings represent a substantial contribution to the field’s understanding of two key issues surrounding ethnic test performance differences. The author calls for a new line of research into these performance facilitating and debilitating factors, before recommendations are offered for practitioners to ensure fairer deployment of ability testing in high-stakes selection processes.

Disentangling patient and public involvement in healthcare decisions:why the difference matters

Patient and public involvement has become an integral aspect of many developed health systems and is judged to be an essential driver for reform. However, little attention has been paid to the distinctions between patients and the public, and the views of patients are often seen to encompass those of the general public. Using an ideal-type approach, we analyse crucial distinctions between patient involvement and public involvement using examples from Sweden and England. We highlight that patients have sectional interests as health service users in contrast to citizens who engage as a public policy agent reflecting societal interests. Patients draw on experiential knowledge and focus on output legitimacy and performance accountability, aim at typical representativeness, and a direct responsiveness to individual needs and preferences. In contrast, the public contributes with collective perspectives generated from diversity, centres on input legitimacy achieved through statistical representativeness, democratic accountability and indirect responsiveness to general citizen preferences. Thus, using patients as proxies for the public fails to achieve intended goals and benefits of involvement. We conclude that understanding and measuring the impact of patient and public involvement can only develop with the application of a clearer comprehension of the differences.

What difference a writing centre makes:a small scale study

Purpose – Academic writing is often considered to be a weakness in contemporary students, while good reporting and writing skills are highly valued by graduate employers. A number of universities have introduced writing centres aimed at addressing this problem; however, the evaluation of such centres is usually qualitative. The paper seeks to consider the efficacy of a writing centre by looking at the impact of attendance on two “real world” quantitative outcomes – achievement and progression. Design/methodology/approach – Data mining was used to obtain records of 806 first-year students, of whom 45 had attended the writing centre and 761 had not. Findings – A highly significant association between writing centre attendance and achievement was found. Progression to year two was also significantly associated with writing centre attendance. Originality/value – Further, quantitative evaluation of writing centres is advocated using random allocation to a comparison condition to control for potential confounds such as motivation.

Does the balanced scorecard make a difference to the strategy development process?

A great number of strategy tools are being taught in strategic management modules. These tools are available to managers for use in facilitating strategic decision-making and enhancing the strategy development process in their organisations. A number of studies have been published examining which are the most popular tools; however there is little empirical evidence on how their utilisation influences the strategy process. This paper is based on a large scale international survey on the strategy development process, and seeks to examine the impact of a particular strategy tool, the Balanced Scorecard, upon the strategy process. The Balanced Scorecard is one of the most popular strategy tools whose use has evolved since its introduction in the 1990’s. Recently, it has been suggested that as a strategy tool, Balanced Scorecard can influence all elements of the strategy process. The results of this study indicate that although there are significant differences in some elements of the strategy process between the organisations that have implemented the Balanced Scorecard and those that have not, the impact is not comprehensive.

Third Ways and new centres - ideological unity or difference?

This chapter illustrates extratextual and intratextual aspects of ideology as related to translation with a case study, a policy document by Tony Blair and Gerhard Schröder, jointly published in English and German in June 1999. Textual features of the two language versions are compared and linked to the social contexts. Concepts and methods of critical discourse analysis and of descriptive and functionalist approaches to translation are applied for this purpose. In particular, reactions to the German text in Germany are explained with reference to the socio-political and ideological conditions of the text production, which was a case of parallel text production combined with translation. It is illustrated that decisions at the linguistic micro-level have had effects for a political party, reflected for example in the German Social Democratic Party debating its identity due to the textual treatment of ideological keywords. The subtle differences revealed in a comparative analysis of the two texts indicate the text producers' awareness of ideological phenomena in the respective cultures. Both texts thus serve as windows onto ideologies and political power relations in the contemporary world.

The effect of interocular phase difference on perceived contrast

Binocular vision is traditionally treated as two processes: the fusion of similar images, and the interocular suppression of dissimilar images (e.g. binocular rivalry). Recent work has demonstrated that interocular suppression is phase-insensitive, whereas binocular summation occurs only when stimuli are in phase. But how do these processes affect our perception of binocular contrast? We measured perceived contrast using a matching paradigm for a wide range of interocular phase offsets (0–180°) and matching contrasts (2–32%). Our results revealed a complex interaction between contrast and interocular phase. At low contrasts, perceived contrast reduced monotonically with increasing phase offset, by up to a factor of 1.6. At higher contrasts the pattern was non-monotonic: perceived contrast was veridical for in-phase and antiphase conditions, and monocular presentation, but increased a little at intermediate phase angles. These findings challenge a recent model in which contrast perception is phase-invariant. The results were predicted by a binocular contrast gain control model. The model involves monocular gain controls with interocular suppression from positive and negative phase channels, followed by summation across eyes and then across space. Importantly, this model—applied to conditions with vertical disparity—has only a single (zero) disparity channel and embodies both fusion and suppression processes within a single framework.