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Potential Biases (potential + biase)
Selected AbstractsPotential biases in sampling design and interpretation of intra-tooth isotope analysisINTERNATIONAL JOURNAL OF OSTEOARCHAEOLOGY, Issue 1-2 2003M. BalasseArticle first published online: 30 JAN 200 Abstract An increasing number of studies dealing with environmental and dietary reconstruction involve measurement of intra-tooth variation of isotope ratios. The sampling procedure typically consists of collecting a sequence of horizontal bands perpendicular to the growth axis of the tooth. The objective is to obtain a temporal sequence of the changes recorded in dental tissues during tooth development. This paper examines some issues associated with this sampling strategy and consequences for interpretation of the data. Time resolution is influenced by the pattern and duration of enamel mineralization, in a way that might, however, depend on the species and the tooth analysed. Although it may be impossible to sample discrete amounts of time, a chronological order seems to be respected, which should be well enough when the objective is to detect changes in isotope ratios with time. Absolute data must be interpreted with caution. Such issues do not affect studies of inter-individual variability as long as the sampling procedure applied to the compared specimens is consistent. A new sampling strategy is tested on modern goat teeth, involving drilling in an oblique direction. The results obtained from obliquely drilled samples are very similar to those obtained from the horizontal sampling procedure. More work is still needed to determine the value of alternative sampling strategies. Copyright © 2003 John Wiley & Sons, Ltd. [source] Family history information on essential tremor: Potential biases related to the source of the casesMOVEMENT DISORDERS, Issue 2 2001Elan D. Louis MD Abstract The proportion of essential tremor (ET) cases that can be attributed to genetic factors is unknown; estimates range from 17,100%. One possible reason for this variability is that clinic and community cases may differ with regard to family history of ET. This is because clinic patients are self-selected and represent as few as 0.5% of all ET cases. Our goal was to determine whether ET cases ascertained from a clinic differed from those ascertained from a community in terms of the family history information that they provided. Subjects (57 clinic, 64 community) underwent a family history interview. Clinic cases were 4.73 times more likely to report an affected relative than were community cases. We conclude that there was a substantial difference between our clinic and community ET cases in terms of the information they provided regarding their family history. Selection and reporting biases could have accounted for this difference. Because of these biases, the source of the cases must be taken into consideration when investigators are trying to synthesize the widely variable results of studies that have estimated the genetic contribution to ET. © 2001 Movement Disorder Society. [source] Potential Errors in Detecting Earnings Management: Reexamining Studies Investigating the AMT of 1986,CONTEMPORARY ACCOUNTING RESEARCH, Issue 4 2001Won W. Choi Abstract In this paper we seek to document errors that could affect studies of earnings management. The book income adjustment (BIA) of the alternative minimum tax (AMT) created apparently strong incentives to manage book income downward in 1987. Five earlier papers using different methodologies and samples all conclude that earnings were reduced in response to the BIA. This consensus of findings offers an opportunity to investigate our speculation that methodological biases are more likely when there appear to be clear incentives for earnings management. A reexamination of these studies uncovers potential biases related to a variety of factors, including choices of scaling variables, selection of affected and control samples, and measurement error in estimated discretionary accruals. A reexamination of the argument underlying these studies also suggests that the incentives to manage earnings are less powerful than initially predicted, and are partially mitigated by tax and non-tax factors. As a result, we believe that the extent of earnings management that occurred in 1987 in response to the BIA remains an unresolved issue. [source] Determining prey distribution patterns from stomach-contents of satellite-tracked high-predators of the Southern OceanECOGRAPHY, Issue 2 2006J. C. Xavier The distribution of many cephalopod, crustacean and fish species in the Southern Ocean, and adjacent waters, is poorly known, particularly during times of the year when research surveys are rare. Analysing the stomach samples of satellite-tracked higher predators has been advocated as a potential method by which such gaps in knowledge can be filled. We examined the viability of this approach through monitoring wandering albatrosses Diomedea exulans at their colony on Bird Island, South Georgia (54°S, 38°W) over the winters (May,July) of 1999 and 2000. At this time, these birds foraged in up to three different water-masses, the Antarctic zone (AZ), the sub-Antarctic zone (SAZ) and the sub-Tropical zone (STZ), which we defined by contemporaneous satellite images of sea surface temperature. A probabilistic model was applied to the tracking and diet data collected from 38 birds to construct a large-scale map of where various prey were captured. Robustness/sensitivity analyses were used to test model assumptions on the time spent foraging and relative catch efficiencies and to evaluate potential biases associated with the model. We were able to predict the distributions of a wide number of cephalopod, crustacean of fish species. We also discovered some of the limitations to using this type of data and proposed ways to rectify these problems. [source] Estimating the number of alcohol-attributable deaths: methodological issues and illustration with French data for 2006ADDICTION, Issue 6 2010Grégoire Rey ABSTRACT Aims Computing the number of alcohol-attributable deaths requires a series of hypotheses. Using French data for 2006, the potential biases are reviewed and the sensitivity of estimates to various hypotheses evaluated. Methods Self-reported alcohol consumption data were derived from large population-based surveys. The risks of occurrence of diseases associated with alcohol consumption and relative risks for all-cause mortality were obtained through literature searches. All-cause and cause-specific population alcohol-attributable fractions (PAAFs) were calculated. In order to account for potential under-reporting, the impact of adjustment on sales data was tested. The 2006 mortality data were restricted to people aged between 15 and 75 years. Results When alcohol consumption distribution was adjusted for sales data, the estimated number of alcohol-attributable deaths, the sum of the cause-specific estimates, was 20 255. Without adjustment, the estimate fell to 7158. Using an all-cause mortality approach, the adjusted number of alcohol-attributable deaths was 15 950, while the non-adjusted estimate was a negative number. Other methodological issues, such as computation based on risk estimates for all causes for ,all countries' or only ,European countries', also influenced the results, but to a lesser extent. Discussion The estimates of the number of alcohol-attributable deaths varied greatly, depending upon the hypothesis used. The most realistic and evidence-based estimate seems to be obtained by adjusting the consumption data for national alcohol sales, and by summing the cause-specific estimates. However, interpretation of the estimates must be cautious in view of their potentially large imprecision. [source] Timing primate evolution: Lessons from the discordance between molecular and paleontological estimatesEVOLUTIONARY ANTHROPOLOGY, Issue 4 2008M. E. Steiper Abstract The molecular clock has become an increasingly important tool in evolutionary biology and biological anthropology. Nevertheless, a source of contention with respect to this method is the frequent discordance with fossil-based estimates of divergence times. The primate radiation is a case in point: Numerous studies have dated the major primate nodes (reviewed in Steiper and Young,1, 2) and there are many instances where molecular and fossil-based estimates of divergence times differ (Fig. 1). Some investigators have recently focused on phenomena such as stratigraphic dating, the stochastic nature of molecular time estimates, and other sources as potential biases in molecular clock estimates.3, 4 In this paper we do not focus on accuracy or statistical error; rather, we argue that discordance is a predictable phenomenon that provides valuable information about the tempo and mode of primate molecular and morphological evolution. Using this perspective, we reexamine the principal theoretical and methodological factors that lead to discordance between molecular and fossil estimates of the origins of taxa and discuss how a better understanding of these factors can help to improve our understanding of primate evolution. [source] Social costs of robbery and the cost-effectiveness of substance abuse treatmentHEALTH ECONOMICS, Issue 8 2008Anirban Basu Abstract Reduced crime provides a key benefit associated with substance abuse treatment (SAT). Armed robbery is an especially costly and frequent crime committed by some drug-involved offenders. Many studies employ valuation methods that understate the true costs of robbery, and thus the true social benefits of SAT-related robbery reduction. At the same time, regression to the mean and self-report bias may lead pre,post comparisons to overstate crime reductions associated with SAT. Using 1992,1997 data from the National Treatment Improvement Evaluation Study (NTIES), we examined pre,post differences in self-reported robbery among clients in five residential and outpatient SAT modalities. Fixed-effect negative binomial regression was used to examine incidence rate reductions (IRR) in armed robbery. Published data on willingness to pay to avoid robbery were used to determine the social valuation of these effects. Differences in IRR across SAT modalities were explored to bound potential biases. All SAT modalities were associated with large and statistically significant reductions in robbery. The average number of self-reported robberies declined from 0.83/client/year pre-entry to 0.12/client/year following SAT (p<0.001). Under worst-case assumptions, monetized valuations of reductions in armed robbery associated with outpatient methadone and residential SAT exceeded economic costs of these interventions. Conventional wisdom posits the economic benefits of SAT. We find that SAT is even more beneficial than is commonly assumed. Copyright © 2007 John Wiley & Sons, Ltd. [source] Testing the convergent validity of the contingent valuation and travel cost methods in valuing the benefits of health careHEALTH ECONOMICS, Issue 2 2002Philip M. Clarke Abstract In this study, the convergent validity of the contingent valuation method (CVM) and travel cost method (TCM) is tested by comparing estimates of the willingness to pay (WTP) for improving access to mammographic screening in rural areas of Australia. It is based on a telephone survey of 458 women in 19 towns, in which they were asked about their recent screening behaviour and their WTP to have a mobile screening unit visit their nearest town. After eliminating missing data and other non-usable responses the contingent valuation experiment and travel cost model were based on information from 372 and 319 women, respectively. Estimates of the maximum WTP for the use of mobile screening units were derived using both methods and compared. The highest mean WTP estimated using the TCM was $83.10 (95% C.I. $99.06,$68.53), which is significantly less than the estimate of $148.09 ($131.13,$166.60) using the CVM. This could be due to the CVM estimates also reflecting non-use values such as altruism, or a range of potential biases that are known to affect both methods. Further tests of validity are required in order to gain a greater understanding of the relationship between these two methods of estimating WTP. Copyright © 2001 John Wiley & Sons, Ltd. [source] Critical review of epidemiological studies of the association between smoking and non-Hodgkin's lymphomaHEMATOLOGICAL ONCOLOGY, Issue 2 2001Hedley G. Peach Abstract Smoking has been suggested to increase the risk of non-Hodgkin's lymphoma (NHL) but the results of epidemiological studies have been inconsistent. The aim of this work was to assess whether the findings of individual studies might have arisen by chance, bias or confounding and whether any associations found between smoking and NHL represent cause-and-effect. Reports of the association between smoking and NHL were identified from Medline. Confidence intervals on relative risks and odds ratios, use of multiple comparisons, and information on source, direction, actual existence and size of potential biases and confounding and features of any associations were abstracted. Four out of five cohort studies found no association between current smoking and NHL but three may have been biased against doing so. One found an association with follicular lymphoma but without a convincing exposure,risk gradient. The fifth found a strong association and an exposure,response gradient with ever smoking but excluded living cases from the end-point. Only one study found an association with past smoking which lacked features of causality. Eight out of 14 case,control studies found no association between current and/or past smoking and NHL but five may have been biased against doing so. Of six positive studies, three involved multiple comparisons, the association of one became non-significant after eliminating bias, four did not explore features of causality and one found an association only in heavy smokers, particularly under 45 years old. There are no grounds to reject the null hypothesis but associations should continue to be sought particularly in subgroups of smokers and with NHL subtypes. Copyright © 2001 John Wiley & Sons, Ltd. [source] Is the Prevalence of Paget's Disease of Bone Decreasing?,JOURNAL OF BONE AND MINERAL RESEARCH, Issue S2 2006Tim Cundy Abstract Secular trends in the severity and prevalence of Paget's disease over a 30-year period are described. Paget's disease has become less prevalent and patients are presenting later, with less severe disease than previously. These data suggest that environmental factors are important in the etiology of Paget's disease. Introduction: Data from several countries support the view that there are important secular trends in the prevalence and severity of Paget's disease. In this paper, recent trends in the epidemiology of Paget's disease are described. Materials and Methods: A database of all newly referred patients (n = 1487) with Paget's disease (1973,2002 inclusive, 30 years) was examined. Of these subjects, 56% had scintiscans. Plasma total alkaline phosphatase (total ALP) activity and disease extent on scintiscan were used as indices of severity. A radiographic prevalence survey of 1019 subjects of European origin >55 years of age in Dunedin was undertaken,,20 years after an earlier survey had shown New Zealand to be a high prevalence area. Results: The number of new referrals with Paget's disease declined sharply from 1994 onward, to one half the rate seen 20 years earlier, whereas the mean age at presentation increased by 4 years per decade (p < 0.0001). Total ALP at diagnosis, disease extent on scintiscan, and the number of bones involved were all negatively correlated with both date of birth (p < 0.0001) and year of presentation (p < 0.0001), indicating that more recently born and presenting subjects had substantially less severe bone disease. The radiographic survey showed that the current prevalence was only ,50% of that in the 1983 survey (p = 0.012). Conclusions: Although there are a number of potential biases, these data are consistent with a continued secular trend to presentation in older subjects with less extensive skeletal involvement and a declining prevalence of Paget's disease. [source] Application of extended inverse scatter correction to mid-infrared reflectance spectra of soilJOURNAL OF CHEMOMETRICS, Issue 5-7 2005Neal B. Gallagher Abstract Scattering artifacts adversely affect infrared reflectance measurements of powders and soils, and extended inverse scatter correction (EISC) is a flexible method useful for correcting these artifacts. EISC was used to correct mid-infrared reflectance spectra of two different soils coated with dibutyl phosphate and the results were examined using regression analysis. To obtain the correction, EISC fits a measured spectrum to a reference spectrum. However, if measured spectra contain features not included in the reference spectrum the fit can be biased resulting in poor correction. Weighted and robust least squares were used to account for these potential biases. Additionally, the present work demonstrates how analyte-free samples can be used to determine basis functions for an extended mixture model used in the correction. Corrected spectra resulted in partial least squares models that performed at least as well as 2nd derivative spectra and were more interpretable. Copyright © 2006 John Wiley & Sons, Ltd. [source] The small mammal community of a coastal site of south-west MauritaniaAFRICAN JOURNAL OF ECOLOGY, Issue 1 2002L. Granjon Abstract The small mammal community of a coastal site of south-western Mauritania was monitored using live trapping, owl pellet analysis and nocturnal visual censuses. Ten species of rodents and two shrews were recorded. Gerbillid rodents (Gerbillus nanus, G. gerbillus, G. tarabuli, G. nigeriae and Taterillus arenarius) were the most prevalent in traps, whereas a relatively large proportion of owl pellets were made up of a murid rodent, Mastomys huberti. The presence of two species of murids (M. huberti and Arvicanthis niloticus) in this presaharian environment is made possible by the presence of small patches of green vegetation associated with localized fresh water inputs. The contradiction of results from the sampling methods indicate potential biases in the determination of community composition and relative species abundance. Results are also discussed in estimating the potential role of predation and competition in this small mammal community. Résumé On a surveillé de façon continue la communauté de petits mammifères d'un site côtier du sud-ouest de la Mauritanie en servant de pièges, de l'analyse des pelotes de réjection des chouettes et de recensements visuels nocturnes. On a rapporté la présence de 10 espèces de rongeurs et de deux musaraignes. Les Gerbillidés (Gerbillus nanus, G. gerbillus, G. tarabuli, G. nigeriae et Taterillus arenarius) étaient ceux qu'on trouvait le plus dans les pièges, alors qu'une assez forte proportion de pelotes étaient constituées des restes d'un rongeur muridé, Mastomys huberti. La présence de deux espèces de muridés (M. huberti et Arvicanthis niloticus) dans cet environnement pré-saharien est rendue possible par de petits îlots de végétation verdoyante associés à des arrivées locales d'eau douce. La contradiction entre les résultats obtenus par les différentes méthodes d'échantillonnage indique la possibilité de biais dans la détermination de la composition de la communauté et l'abondance relative des espèces. On discute aussi les résultats en estimant le rôle potentiel de la prédation et de la compétition dans cette communauté de petits mammifères. [source] Studying aggression in school children: The use of a wireless microphone and micro-video cameraAGGRESSIVE BEHAVIOR, Issue 5 2002Katy Tapper Abstract This paper describes a wireless microphone and micro-video camera used successfully by the present authors to study direct, indirect, and relational forms of aggression in schools. Two major advantages of this equipment are identified; first, it avoids some of the potential biases and difficulties associated with the other methods and, second, it allows researchers to record and analyze a large number of significant variables that may otherwise be difficult to assess. The importance of this kind of data is discussed in relation to the development of effective interventions aimed at reducing aggression in schools. Aggr. Behav. 28:356,365, 2002. © 2002 Wiley-Liss, Inc. [source] Determining if disease management saves money: an introduction to meta-analysisJOURNAL OF EVALUATION IN CLINICAL PRACTICE, Issue 3 2007Ariel Linden DrPH MS Abstract Disease management (DM) programmes have long been promoted as a major medical cost-saving mechanism, even though the scant research that exists on the topic has provided conflicting results. In a 2004 literature review, the Congressional Budget Office stated that ,there is insufficient evidence to conclude that disease management programs can generally reduce the overall cost of health care services'. To address this question more accurately, a meta-analysis was warranted. Meta-analysis is the quantitative technique used to pool the results of many studies on the same topic and summarize them statistically. This method is also quite suitable for individual DM firms to assess whether their programmes are effective at the aggregate level. This paper describes the elements of a rigorous meta-analytic process and discusses potential biases. A hypothetical DM organization is then evaluated with a specific emphasis on medical cost-savings, simulating a case in which different populations are served, evaluation methodologies are employed, and diseases are managed. [source] International Differences in Nursing Research, 2005,2006JOURNAL OF NURSING SCHOLARSHIP, Issue 1 2009Denise F. Polit PhD Abstract Purpose: To compare the characteristics of nursing research being done in different countries, using data from studies published in nonspecialty, English-language nursing journals. Design: Data for this cross-sectional analysis were retrieved from a consecutive sample of 1,072 studies published in eight leading English-language research journals in 2005 and 2006. Methods: For each study, data were extracted on the characteristics of the study participants and authors, study focus-specialty area, funding, and methodologic attributes. Studies from 15 countries or regional groupings were compared. Findings: International differences in authors, participants, and study characteristics were typically large and statistically significant. Studies that were focused on nurses were especially prevalent in Europe, Australia, and Canada, whereas patient-centered studies were most common in Asian countries and the US. Qualitative studies were predominant in Norway, Sweden, and the UK. Asian nurse researchers, by contrast, undertook mostly quantitative studies, and were especially likely to conduct intervention research. Significant country differences existed in the omission of demographic (age and sex) information about participants, with omissions most prevalent in the UK and Ireland and least prevalent in Asian countries. Research funding was reported for 62% of all studies, ranging from 13% in Turkey to over 75% in Canada and the US. Conclusions: Although this study had several limitations, especially with regard to potential biases in the sample of studies from non-English-speaking countries, this analysis of over 1,000 nursing studies indicates many important inter-country differences in the focus, methods, and authorship patterns of nursing research published in leading journals. Clinical Relevance: Because research "informs" practice, international differences that exist in the focus and methods of nursing research have implications for nursing practice in the respective countries. [source] THE EFFECTS OF PERSONALITY SIMILARITY ON PEER RATINGS OF CONTEXTUAL WORK BEHAVIORSPERSONNEL PSYCHOLOGY, Issue 2 2001DAVID ANTONIONI The present field study investigates whether rater-ratee similarity in the Big Five personality factors influences peer ratings of contextual work behaviors. It overcomes problems that previous studies have had by using a polynomial regression analysis and by correcting the potential biases from nonindependence. Using more than 500 peer dyads, we found that rater-ratee similarity in Conscientiousness, but not in other dimensions, was positively associated with peer ratings even after controlling for interpersonal affect. These results suggest that the observed effect of personality similarity may reflect actual behavioral differences rather than biases due to interpersonal affect. Implications of the findings are discussed along with recommendations for future research. [source] Unmet Need Among Rural Medicaid Beneficiaries in MinnesotaTHE JOURNAL OF RURAL HEALTH, Issue 3 2002Sharon K. Long Ph.D. Given the vulnerabilities of rural residents and the health care issues faced by the Medicaid population generally, the combined effects of being on Medicaid and living in a rural area raise important questions about access to health care services. This study looks at a key dimension of health care access: unmet need for health care services. The study relies on data from a 1998 survey of rural Minnesota Medicaid beneficiaries. An overall response rate of 70% was obtained. For this study, the sample is limited to women who were on Medicaid for the full 12 months prior to the survey, resulting in 900 respondents. The study finds that the rural Medicaid beneficiaries face high levels of unmet need: more than 1 in 3 reported either delaying or not getting doctor, hospital, or specialist care that they felt they needed. Although the study lacks direct measures of the consequences of the high levels of unmet need, there is evidence that greater emergency room use is associated with unmet need. The survey data cannot necessarily be generalized to other rural areas, and like all surveys, this one is subject to nonresponse bias as well as potential biases because of respondent recall and self-assessment of medical needs. Nevertheless, these findings are suggestive of negative consequences of unmet need for both Medicaid beneficiaries and program costs. [source] Study Designs and Evaluation Models for Emergency Department Public Health ResearchACADEMIC EMERGENCY MEDICINE, Issue 11 2009Kerry B. Broderick MD Abstract Public health research requires sound design and thoughtful consideration of potential biases that may influence the validity of results. It also requires careful implementation of protocols and procedures that are likely to translate from the research environment to actual clinical practice. This article is the product of a breakout session from the 2009 Academic Emergency Medicine consensus conference entitled "Public Health in the ED: Screening, Surveillance, and Intervention" and serves to describe in detail aspects of performing emergency department (ED)-based public health research, while serving as a resource for current and future researchers. In doing so, the authors describe methodologic features of study design, participant selection and retention, and measurements and analyses pertinent to public health research. In addition, a number of recommendations related to research methods and future investigations related to public health work in the ED are provided. Public health investigators are poised to make substantial contributions to this important area of research, but this will only be accomplished by employing sound research methodology in the context of rigorous program evaluation. [source] Biases associated with population estimation using molecular taggingANIMAL CONSERVATION, Issue 3 2000Juliann L. Waits Although capture,recapture techniques are often used to estimate population size, these approaches are difficult to implement for a wide variety of species. Highly polymorphic microsatellite markers are useful in individual identification, and these ,molecular tags' can be collected without having to capture or trap the individual. However, several sources of error associated with molecular identification techniques, including failure to identify individuals with the same genotype for these markers as being different, and incorrect assignment of individual genotypes, could bias population estimates. Simulations of populations sampled for the purpose of estimating population size were used to assess the extent of these potential biases. Population estimates tended to be biased downward as the likelihood of individuals sharing the same genotype increased (as measured by the probability of identity (PI) of the multi-locus genotype); this bias increased with population size. Populations of 1000 individuals were underestimated by ,5% when the PI was as small as 1.4 × 10,7. A similar-sized bias did not occur for populations of 50 individuals until the PI had increased to approximately 2.5 × 10,5. Errors in genotype assignment resulted in overestimates of population size; this problem increased with the number of samples and loci that were genotyped. Population estimates were often >200% the size of the simulated populations when the probability of making a genotyping error was 0.05/locus and 7,10 loci were used to identify individuals. This bias was substantially reduced by decreasing genotyping error rate to 0.005. If possible, only highly polymorphic loci that are critical for the identification of the individual should be used in molecular tagging, and considerable efforts should be made to minimize errors in genotype determination. [source] A survey of people's attitudes and beliefs about false confessionsBEHAVIORAL SCIENCES & THE LAW, Issue 5 2008Linda A. Henkel Ph.D. The attitudes and beliefs of jury eligible individuals regarding false confessions were investigated in order to uncover potential biases. Survey respondents provided perceptions of factors related to false confessions (e.g. their frequency and likely situational and dispositional risk variables). Results indicate that people possess an awareness that false confessions can occur and believe that a confession should not be taken as an absolute indicator of guilt. However, their understanding of predisposing and situational factors that contribute to false confessions was incomplete, as was their understanding of interrogation practices. Furthermore, respondents showed a marked bias against believing that they personally would ever falsely confess, which is discussed in the context of potential inconsistencies between people's self-report and their actual behaviors in naturalistic situations. Copyright © 2008 John Wiley & Sons, Ltd. [source] Les hedge funds ont-ils leur place dans un portefeuille institutionnel canadien?CANADIAN JOURNAL OF ADMINISTRATIVE SCIENCES, Issue 3 2003Stéphanie Desrosiers This article examines the return and risk of hedge funds (HF), and their correlations with traditional asset classes for the 1990,2002 period. Efficient frontiers resulting from optimizations with and without constraints demonstrate that it is worthwhile to include HF in a Canadian institutional investor's portfolio. HF offer a high potential return relative to risk, while weaker correlations with traditional asset classes create a beneficial diversification effect. Non-directional HF provide protection in bear markets and are more suitable for lower risk portfolios, whereas directional HF are better suited to higher risk portfolios. Caveats are necessary due to the skew-ness and kurtosis of the return distributions, potential biases in the return series, the lower liquidity, and the complexity of the HF industry. Résumé Cet article examine le rendement, le risque et les correélations des hedge funds (HF) avec les catégories d'actif traditionnelles sur la période 1990,2002. Des optimisations avec et sans contraintes montrent qu'il est avantageux d'inclure les HF dans un portefeuille institutionnel canadien du fait d'un potentiel de rendement élevé par rapport au risque encouru et de faibles corrélations. Les HF non-directionnels offrent une meilleure protection en marché baissier et sont plus appropriés pour des portefeuilles moins risqués. Les HF directionnels conviennent davantage aux portefeuilles prksentant un risque plus élevé. Des réserves doivent toutefois étre émises en raison des coefficients d'asymétrie et d'aplatissement de la distribution des rendements, des biais potentiels des données, de la faible liquidité, et de la complexité de l'industrie des HF. [source] | ||||||||||||||||||||||