Influence of data display formats on physician investigators' decisions to stop clinical trials: prospective trial with repeated measures.
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OBJECTIVE: To examine the effect of the method of data display on physician investigators' decisions to stop hypothetical clinical trials for an unplanned statistical analysis. DESIGN: Prospective, mixed model design with variables between subjects and within subjects (repeated measures). SETTING: Comprehensive cancer centre. PARTICIPANTS: 34 physicians, stratified by academic rank, who were conducting clinical trials. INTERVENTIONS: PARTICIPANTS were shown tables, pie charts, bar graphs, and icon displays containing hypothetical data from a clinical trial and were asked to decide whether to continue the trial or stop for an unplanned statistical analysis. MAIN OUTCOME MEASURE: Percentage of accurate decisions with each type of display. RESULTS: Accuracy of decisions was affected by the type of data display and positive or negative framing of the data. More correct decisions were made with icon displays than with tables, pie charts, and bar graphs (82% v 68%, 56%, and 43%, respectively; P=0.03) and when data were negatively framed rather than positively framed in tables (93% v 47%; P=0.004). CONCLUSIONS: Clinical investigators' decisions can be affected by factors unrelated to the actual data. In the design of clinical trials information systems, careful consideration should be given to the method by which data are framed and displayed in order to reduce the impact of these extraneous factors. (+info)
A web exercise in evidence-based medicine using cognitive theory.
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Our aim was to improve clinical reasoning skills by applying an established theory of memory, cognition, and decision making (fuzzy-trace theory) to instruction in evidence-based medicine. Decision-making tasks concerning chest pain evaluation in women were developed for medical students and internal medicine residents. The fuzzy-trace theory guided the selection of online sources (e.g., target articles) and decision-making tasks. Twelve students and 22 internal medicine residents attended didactic conferences emphasizing search, evaluation, and clinical application of relevant evidence. A 17-item Likert scale questionnaire assessed participants' evaluation of the instruction. Ratings for each of the 17 items differed significantly from chance in favor of this alternative approach to instruction. We concluded that fuzzy-trace theory may be a useful guide for developing learning exercises in evidence-based medicine. (+info)
Stopping rules for phase II studies.
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This paper, the second in a series of three papers concerned with the statistical aspects of interim analyses in clinical trials, is concerned with stopping rules in phase II clinical trials. Phase II trials are generally small-scale studies, and may include one or more experimental treatments with or without a control. A common feature is that the results primarily determine the course of further clinical evaluation of a treatment rather than providing definitive evidence of treatment efficacy. This means that there is more flexibility available in the design and analysis of such studies than in phase III trials. This has led to a range of different approaches being taken to the statistical design of stopping rules for such trials. This paper briefly describes and compares the different approaches. In most cases the stopping rules can be described and implemented easily without knowledge of the detailed statistical and computational methods used to obtain the rules. (+info)
The economics of 'more research is needed'.
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BACKGROUND: Results from epidemiology and other health research affect millions of life-years and billions of dollars, and the research directly consumes millions of dollars. Yet we do little to assess the value of research projects for future policy, even amid the ubiquitous assertions that 'more research is necessary' on a given topic. This methodological proposal outlines the arguments for why and how ex ante assessments can inform us about the value of a particular piece of further research on a topic. METHODS: Economics and decision theory concepts-cost-benefit analysis and probability-weighted predictions of outcomes-allow us to calculate the payoff from applied health research based on resulting decisions. Starting with our probability distribution for the parameters of interest, a Monte Carlo simulation generates the distribution of outcomes from a particular new study. Each true value and outcome are associated with a policy decision, and improved decisions are valued to give us the study's contribution as applied research. RESULTS: The analysis demonstrates how to calculate the expected value of further research, for a simplified case, and assess whether it is really warranted. Perhaps more important, it points out what the measure of the value of a further study ought to be. CONCLUSIONS: It is quite possible to improve our technology for assessing the value of particular pieces of further research on a topic. However, this will only happen if the need and possibility are recognized by methodologists and applied researchers. (+info)
Caudate clues to rewarding cues.
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Behavioral studies indicate that prior experience can influence discrimination of subsequent stimuli. The mechanisms responsible for highlighting a particular aspect of the stimulus, such as motion or color, as most relevant and thus deserving further scrutiny, however, remain poorly understood. In the current issue of Neuron, demonstrate that neurons in the caudate nucleus of the basal ganglia signal which dimension of a visual cue, either color or location, is associated with reward in an eye movement task. These findings raise the possibility that this structure participates in the reward-based control of visual attention. (+info)
Managing toxic thyroid adenoma: a cost-effectiveness analysis.
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OBJECTIVE: To examine the cost-effectiveness of therapeutic strategies for patients with toxic thyroid adenoma. DESIGN: A decision analytic model was used to examine strategies, including thyroid lobectomy after a 3-month course of antithyroid drugs (ATDs), radioactive iodine (RAI), and lifelong ATDs followed by either RAI (ATD-RAI) or surgery (ATD-surgery) in patients suffering severe drug reactions. METHODS: Outcomes were measured in quality-adjusted life years. Data on the prevalence of co-incident thyroid cancer, complications and treatment efficacies were derived from a systematic review of the literature (1966-2000). Costs were examined from the health care system perspective. Costs and effectiveness were examined at their present values. Discounting (3% per year), variations of major cost components, and every variable for which disagreements exist among studies or expert opinion were examined by sensitivity analyses. RESULTS: For a 40-year-old woman, surgery was both the most effective and the least costly strategy (Euro 1391),while ATD-RAI cost the most (Euro 5760). RAI was more effective than surgery if surgical mortality exceeded 0.6% (base-case 0.001%). RAI become less costly for women of more than 72 years (more than 66 in discounted analyses). For women of 85, ATD-RAI may be more effective than RAI and have an inexpensive marginal cost-effectiveness ratio (Euro 4975) if lifelong follow-up results in no decrement in quality of life. CONCLUSIONS: Age, surgical mortality, therapeutic costs and patient preference must all be considered in choosing an appropriate therapy. (+info)
Disambiguating ambiguous biomedical terms in biomedical narrative text: an unsupervised method.
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With the growing use of Natural Language Processing (NLP) techniques for information extraction and concept indexing in the biomedical domain, a method that quickly and efficiently assigns the correct sense of an ambiguous biomedical term in a given context is needed concurrently. The current status of word sense disambiguation (WSD) in the biomedical domain is that handcrafted rules are used based on contextual material. The disadvantages of this approach are (i) generating WSD rules manually is a time-consuming and tedious task, (ii) maintenance of rule sets becomes increasingly difficult over time, and (iii) handcrafted rules are often incomplete and perform poorly in new domains comprised of specialized vocabularies and different genres of text. This paper presents a two-phase unsupervised method to build a WSD classifier for an ambiguous biomedical term W. The first phase automatically creates a sense-tagged corpus for W, and the second phase derives a classifier for W using the derived sense-tagged corpus as a training set. A formative experiment was performed, which demonstrated that classifiers trained on the derived sense-tagged corpora achieved an overall accuracy of about 97%, with greater than 90% accuracy for each individual ambiguous term. (+info)
The structure of pigeon multiple-class same-different learning.
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Three experiments examined the structure of the decision framework used by pigeons in learning a multiple-class same-different task. Using a same-different choice task requiring the discrimination of odd-item different displays (one or more of the display's component elements differed) from same displays (all display components identical), pigeons were concurrently trained with sets of four discriminable display types. In each experiment, the consistent group was tested such that the same and different displays of four display types were consistently mapped onto their choice alternatives. The inconsistent group received a conflicting mapping of the same and different displays and the choice alternatives that differed across the four display types but were consistent within a display type. Experiment 1 tested experienced pigeons, and Experiment 2 tested naive pigeons. In both experiments, the consistent group learned their discrimination faster and to a higher level of choice accuracy than did the inconsistent group, which performed poorly in general. Only in the consistent group was the discrimination transferred to novel stimuli, indicative of concept formation in that group. A third experiment documented that the different display classes were discriminable from one another. These results suggest that pigeons attempt to generate a single discriminative rule when learning this type of task, and that this general rule can cover a large variety of stimulus elements and organizations, consistent with previous evidence suggesting that pigeons may be capable of learning relatively unbounded relational same-different concepts. (+info)