44 resultados para item response theory

em Aston University Research Archive


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Purpose - This paper provides a deeper examination of the fundamentals of commonly-used techniques - such as coefficient alpha and factor analysis - in order to more strongly link the techniques used by marketing and social researchers to their underlying psychometric and statistical rationale. Design/methodology approach - A wide-ranging review and synthesis of psychometric and other measurement literature both within and outside the marketing field is used to illuminate and reconsider a number of misconceptions which seem to have evolved in marketing research. Findings - The research finds that marketing scholars have generally concentrated on reporting what are essentially arbitrary figures such as coefficient alpha, without fully understanding what these figures imply. It is argued that, if the link between theory and technique is not clearly understood, use of psychometric measure development tools actually runs the risk of detracting from the validity of the measures rather than enhancing it. Research limitations/implications - The focus on one stage of a particular form of measure development could be seen as rather specialised. The paper also runs the risk of increasing the amount of dogma surrounding measurement, which runs contrary to the spirit of this paper. Practical implications - This paper shows that researchers may need to spend more time interpreting measurement results. Rather than simply referring to precedence, one needs to understand the link between measurement theory and actual technique. Originality/value - This paper presents psychometric measurement and item analysis theory in easily understandable format, and offers an important set of conceptual tools for researchers in many fields. © Emerald Group Publishing Limited.

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The convergence on the Big Five in personality theory has produced a demand for efficient yet psychometrically sound measures. Therefore, five single-item measures, using bipolar response scales, were constructed to measure the Big Five and evaluated in terms of their convergent and off-diagonal divergent properties, their pattern of criterion correlations and their reliability when compared with four longer Big Five measures. In a combined sample (N?=?791) the Single-Item Measures of Personality (SIMP) demonstrated a mean convergence of r?=?0.61 with the longer scales. The SIMP also demonstrated acceptable reliability, self–other accuracy, and divergent correlations, and a closely similar pattern of criterion correlations when compared with the longer scales. It is concluded that the SIMP offer a reasonable alternative to longer scales, balancing the demands of brevity versus reliability and validity.

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Cet article présente une synthèse des recherches et théories qui éclairent notre compréhension de la créativité et de la mise en oeuvre de l’innovation dans les groupes de travail. Il semble que la créativité apparaisse essentiellement au cours des premières étapes du processus, avant la mise en oeuvre. On étudie l’influence des caractéristiques de la tâche, des capacités et de l’éventail des connaissances du groupe, des demandes externes, des mécanismes d’intégration et de cohérence de groupe. La perception d’une menace, l’incertitude ou de fortes exigences entravent la créativité, mais favorisent l’innovation. La diversité des connaissances et des capacités est un bon prédicteur de l’innovation, mais l’intégration du groupe et les compétences sont indispensables pour récolter les fruits de la diversité. On examine aussi les implications théoriques et pratiques de ces considérations. In this article I synthesise research and theory that advance our understanding of creativity and innovation implementation in groups at work. It is suggested that creativity occurs primarily at the early stages of innovation processes with innovation implementation later. The influences of task characteristics, group knowledge diversity and skill, external demands, integrating group processes and intragroup safety are explored. Creativity, it is proposed, is hindered whereas perceived threat, uncertainty or other high levels of demands aid the implementation of innovation. Diversity of knowledge and skills is a powerful predictor of innovation, but integrating group processes and competencies are needed to enable the fruits of this diversity to be harvested. The implications for theory and practice are also explored.

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The latency variation of the P100M from minute to minute, between morning and afternoon and from day to day was investigated in an unshielded environment using two single channel magnetometers. Latency variation was greatest from minute to minute with relatively little longer term variation. The two magnetometers differed both in mean latency and in the degree of variation. This may be attributed to variation in the performance of the filters which were set a narrow bandwidth for recording in an unshielded environment.

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A decrease in the check size of a pattern shift stimulus increases the latency and amplitude of the visual evoked potential (VEP) P100. In addition, for a given check size, decreasing the size of the stimulus field increases the latency and amplitude of the P100. These results imply that the central regions of the retina make a significant contribution to the generation of the electrical P100. However, the corresponding magnetic P100m may have a different origin. We have studied the effects of check and field size on the P100m in five normal subjects using a DC-Squid, second-order gradiometer. Magnetic responses were recorded at the positive maximum of the P100m over the occipital scalp to six check sizes (10-100') presented in a large (13 degrees 34') and small (5 degrees 14') field and to a large check (100') presented in seven field sizes (1 degree 45' - 15 degrees 10'). No responses were recorded to any check size with a small field. Decreasing the check size presented in a large field increased latency of the P100m by approx. 30 ms while the amplitude of the response decreased with the largest reduction occurring between 70' and 12' checks. Using a large check, latency increased and amplitude decreased as the field size was reduced. The latency changes in response to check and field size were similar to those described for the VEP although the magnitudes of the magnetic changes were greater. Unlike the VEP, amplitude responses were maximal when large checks were presented in a large stimulus field. This suggests that regions outside the central retina make a more significant contribution to the visual evoked magnetic response than they do to the VEP, and that the P100m may be useful clinically in the study of diseases that affect the more peripheral regions of the retina.

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The topography of the visual evoked magnetic response to a pattern onset stimulus was studied in four normal subjects. The topography of th CIIm component was consistent when measured on the same subject nine months apart. Full field responses were more variable than half field responses. With decreasing check size, the field pattern changes from a simple distribution with one outgoing and one ingoing area of field to a more complex pattern with in and outgoing fields over each hemisphere of the brain. The source may originate at the pole or from within the calcarine fissure.

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The visual evoked magnetic response to half-field stimulation using pattern reversal was studied using a dc-SQUID coupled to a second-order gradiometer. The main component of the magnetic response consisted of a positive wave at around 100ms (P100M). At the same time this component was present the reponse to half-field stimulation consisted of an outgoing field contralateral and extending to the midline. When the left half-field was stimulates the outgoing field was over the posterior right visual cortex and when the right half field was stimulated it was over the left anterior visual cortex. These findings would correltly identify a source located in the contralateral visual cortex. The orientation of the dipoles was not that previously assumed to explain the paradoxical lateralization of the visual evoked potential. The results are discussed in terms of both electrical and magnetic models of the calcarine fissure.

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Electrical compound action potentials (ECAPs) of the cochlear nerve are used clinically for quick and efficient cochlear implant parameter setting. The ECAP is the aggregate response of nerve fibres at various distances from the recording electrode, and the magnitude of the ECAP is therefore related to the number of fibres excited by a particular stimulus. Current methods, such as the masker-probe or alternating polarity methods, use the ECAP magnitude at various stimulus levels to estimate the neural threshold, from which the parameters are calculated. However, the correlation between ECAP threshold and perceptual threshold is not always good, with ECAP threshold typically being much higher than perceptual threshold. The lower correlation is partly due to the very different pulse rates used for ECAPs (below 100 Hz) and clinical programs (hundreds of Hz up to several kHz). Here we introduce a new method of estimating ECAP threshold for cochlear implants based upon the variability of the response. At neural threshold, where some but not all fibers respond, there is a different response each trial. This inter-trial variability can be detected overlaying the constant variability of the system noise. The large stimulus artefact, which requires additional trials for artefact rejection in the standard ECAP magnitude methods, is not consequential, as it has little variability. The variability method therefore consists of simply presenting a pulse and recording the ECAP, and as such is quicker than other methods. It also has the potential to be run at high rates like clinical programs, potentially improving the correlation with behavioural threshold. Preliminary data is presented that shows a detectable variability increase shortly after probe offset, at probe levels much lower than those producing a detectable ECAP magnitude. Care must be taken, however, to avoid saturation of the recording amplifier saturation; in our experiments we found a gain of 300 to be optimal.