|
|
|
| Registros recuperados: 14 | |
|
|
| Orsini, Nicola; Bellocco, Rino; Bottai, Matteo; Wolk, Alicja; Greenland, Sander. |
| Classification errors, selection bias, and uncontrolled confounders are likely to be present in most epidemiologic studies, but the uncertainty introduced by these types of biases is seldom quantified. The authors present a simple yet easy-to-use Stata command to adjust the relative risk for exposure misclassification, selection bias, and an unmeasured confounder. This command implements both deterministic and probabilistic sensitivity analysis. It allows the user to specify a variety of probability distributions for the bias parameters, which are used to simulate distributions for the bias-adjusted exposure–disease relative risk. We illustrate the command by applying it to a case–control study of occupational resin exposure and lung-cancer deaths. By... |
| Tipo: Article |
Palavras-chave: Episens; Episensi; Sensitivity analysis; Unmeasured confounder; Misclassification; Bias; Epidemiology; Research Methods/ Statistical Methods. |
| Ano: 2008 |
URL: http://purl.umn.edu/120927 |
| |
|
| |
|
|
| Hink, Matthew J.; Cardwell, Ryan T.; Lawley, Chad. |
| There exists an extensive literature that attempts to identify important factors that determine trade policies. An understanding of these important factors could be useful when negotiating trade agreements, especially in agriculture, which is a relatively heavily supported industry. Limao and Panagariya (L&P, 2007) modify Grossman and Helpman’s (G&H, 1994) lobbying model in an attempt to understand why anti-trade bias (as opposed to pro-trade bias, which is predicted by the G&H (1994) model) is the predominant pattern in observed trade policy. L&P (2007) propose that governments seek to reduce inequality between sectors by modifying trade policies in a way that reallocates gross revenue from the larger to the smaller sector. We use measures... |
| Tipo: Working Paper |
Palavras-chave: Trade; Policy; Bias; Agricultural and Food Policy; International Relations/Trade. |
| Ano: 2012 |
URL: http://purl.umn.edu/122739 |
| |
|
|
| Trenkel, Verena; Cotter, John. |
| Ecosystem assessments of fisheries based only on survey data will often have to use surveys that were designed historically for special purposes, e. g. for assessing abundances of two or three target species, or for tuning VPAs. An important question then is whether the previously collected data can provide informative time series of abundance indices and other state indicators for a wider range of target and non-target species. Some potential shortcomings of existing data series are treated in this paper leading to four questions which can guide the user to determine the suitability of an existing time series: did the survey cover the stock of each species adequately? Did survey catchability vary significantly between length or age classes? Did survey... |
| Tipo: Text |
Palavras-chave: Bias; Survey based methods; Indicators. |
| Ano: 2009 |
URL: http://archimer.ifremer.fr/doc/2009/publication-6900.pdf |
| |
|
|
| Petitgas, Pierre; Goarant, Anne; Masse, Jacques; Bourriau, Paul. |
| Petitgas, P., Goarant, A., Masse, J., and Bourriau, P. 2009. Combining acoustic and CUFES data for the quality control of fish-stock survey estimates. - ICES Journal of Marine Science, 66: 1384-1390. |
| Tipo: Text |
Palavras-chave: CUFES; Biscay; Bias; Anchovy; Acoustics; Abundance. |
| Ano: 2009 |
URL: http://archimer.ifremer.fr/doc/2009/publication-6566.pdf |
| |
|
| |
|
|
| Foster, Scott D.; Vanhatalo, Jarno; Trenkel, Verena; Schulz, Torsti; Lawrence, Emma; Przeslawski, Rachel; Hosack, Geoffrey R.. |
| Data are currently being used, and reused, in ecological research at an unprecedented rate. To ensure appropriate reuse however, we need to ask the question: “Are aggregated databases currently providing the right information to enable effective and unbiased reuse?” We investigate this question, with a focus on designs that purposefully favour the selection of sampling locations (upweighting the probability of selection of some locations). These designs are common and examples are those designs that have uneven inclusion probabilities or are stratified. We perform a simulation experiment by creating datasets with progressively more uneven inclusion probabilities, and examine the resulting estimates of the average number of individuals per unit area... |
| Tipo: Text |
Palavras-chave: Bias; Survey Design; Database; Population Density Estimate; Model; Horvitz‐Thompson; FAIR; Reuse; Data; Inclusion Probability. |
| Ano: 2021 |
URL: https://archimer.ifremer.fr/doc/00691/80339/83422.pdf |
| |
|
|
| Battaglia, Andre; Trenkel, Verena; Rochet, Marie-joelle. |
| The end effect in trawl catches is defined as the proportion of the fish catch taken during shooting and hauling of the net, a period excluded from that nominally referred to as haul duration. If important, this effect will lead to biased abundance estimates, because the swept area will be underestimated. An experimental survey was carried out to compare catch numbers obtained in standard research 30-min hauls with those from 0-min hauls, the latter referring to the trawl being hauled as soon as the trawl geometry stabilized on the seabed. Average catch ratios (0-min/30-min hauls) ranged from 0.05 (s.d. 0.06) for sole to 0.34 (s.d. 0.64) for hake, indicating that the end effect might be more important and more variable for highly mobile species. As a... |
| Tipo: Text |
Palavras-chave: Trawl survey; Bias; Abundance index. |
| Ano: 2006 |
URL: https://archimer.ifremer.fr/doc/2006/publication-1686.pdf |
| |
|
|
| Diner, Noel. |
| The aggregate backscattering cross-section, sag, is the sum of backscattering cross-sections of all fish in a shoal. It is a basic acoustical parameter used for shoal description and biomass estimation. Simulations were undertaken for evaluating the impact of horizontal dimension, density, depth and beam width on measurements of sag for shoals with constant abundance. The important factor determining measurement bias is the ratio of shoal size expressed as along cross-section length relative to along ship beam width at mean shoal depth. The results show that 10 log10(sag) is underestimated by about 8 dB for a 5 m long shoal located at 200 m depth if detected by a 7? beam. A formula for correcting sag estimates for shoal sizes bigger than 1.3 times the beam... |
| Tipo: Text |
Palavras-chave: Shoal dimension; Shoal energy; Single beam echosounder; Acoustic measurements; Accuracy; Bias. |
| Ano: 2007 |
URL: http://archimer.ifremer.fr/doc/2007/publication-2583.pdf |
| |
|
|
| Morais,L.; Bosco,A.M.; Baptisttiolli,L.; Torrecilha,R.B.P.; Valadares,T.C.; Hoffmann,D.J.; Ciarlini,P.C.. |
| RESUMO Considerando que, entre todas as fontes de erro analítico, a hemólise é a mais importante na rotina laboratorial, o presente estudo teve como objetivo investigar o efeito da hemólise in vitro sobre os principais biomarcadores plasmáticos de estresse oxidativo mensurados (BPEO) de cães. Para tal, amostras de sangue total de 19 cães clinicamente saudáveis foram hemolisadas em diferentes graus por ação mecânica. Amostras controle contendo baixa concentração de hemoglobina (Hb) no plasma foram comparadas com quatro graus de hemólise (<0,36; 0,36-0,60; 0,61-1,0; 1,1-4g/L Hb). Imediatamente após a hemólise, foram mensuradas as concentrações plasmáticas de ácido úrico (AU), albumina, bilirrubina, gamaglutamiltransferase (GGT), capacidade antioxidante... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Antioxidante; Bias; Erro analítico; Hemoglobina; Oxidante. |
| Ano: 2018 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0102-09352018000300713 |
| |
|
| |
|
|
| Yasar, Mahmut; Raciborski, Rafal; Poi, Brian P.. |
| Productivity is often computed by approximating the weighted sum of the inputs from the estimation of the Cobb–Douglas production function. Such estimates, however, may suffer from simultaneity and selection biases. Olley and Pakes (1996, Econometrica 64: 1263–1297) introduced a semiparametric method that allows us to estimate the production function parameters consistently and thus obtain reliable productivity measures by controlling for such biases. This study first reviews this method and then introduces a Stata command to implement it. We show that when simultaneity and selection biases are not controlled for, the coefficients for the variable inputs are biased upward and the coefficients for the fixed inputs are biased downward. |
| Tipo: Article |
Palavras-chave: Opreg; Levpet; Production function; Bias; Simultaneity; Research Methods/ Statistical Methods. |
| Ano: 2008 |
URL: http://purl.umn.edu/122587 |
| |
|
|
| Kragt, Marit Ellen; Bennett, Jeffrey W.. |
| Choice Experiments (CE) are increasingly used to estimate the values of environmental goods and services. CE questionnaires represent the environmental good under valuation by varying levels of non-market attributes. Inclusion of a cost attribute enables the estimation of monetary values for changes in the non-market attributes presented. The ways in which the levels of the attributes are described in the survey - the ‘attribute frame’ - may affect respondents’ choices. Furthermore, varying levels of the cost attribute may impact CE value estimates. The challenge for CE practitioners is to identify the ‘appropriate’ attribute frames and cost levels. In this paper, the impacts of changing cost levels and the impacts of describing non-market attributes as... |
| Tipo: Conference Paper or Presentation |
Palavras-chave: Choice Experiments; Environmental Valuation; Bias; Tasmania; Environmental Economics and Policy. |
| Ano: 2010 |
URL: http://purl.umn.edu/59091 |
| |
|
| |
| Registros recuperados: 14 | |
|
|
|
