52 resultados para MCMC sampling


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Gambling prevalence studies are typically conducted within a single (landline) telephone sampling frame. This practice continues, despite emerging evidence that significant differences exist between landline and mobile (cell) phone only households. This study utilised a dual-frame (landline and mobile) telephone sampling methodology to cast light on the extent of differences across groups of respondents in respect to demographic, health, and gambling characteristics.

A total of 2,014 participants from across Australian states and 
territories ranging in age from 18 to 96 years participated. Interviews were conducted using computer assisted telephone interviewing technology where 1,012 respondents from the landline sampling frame and 1,002 from the mobile phone sampling frame completed a questionnaire about gambling and other health behaviours. Responses across the landline sampling frame, the mobile phone sampling frame, and the subset of the mobile phone sampling frame that possessed a mobile phone only (MPO) were contrasted.

The findings 
revealed that although respondents in the landline sample (62.7 %) did not significantly differ from respondents in the mobile phone sample (59.2 %) in gambling participation in the previous 12 months, they were significantly more likely to have gambled in the previous 12 months than the MPO sample (56.4 %). There were no significant differences in internet gambling participation over the previous 12 months in the landline sample (4.7 %), mobile phone sample (4.7 %) and the MPO sample (5.0 %). However, endorsement of lifetime problem gambling on the NODS-CLiP was significantly higher within the mobile sample (10.7 %) and the MPO sample (14.8 %) than the landline sample (6.6 %).

Our research 
supports previous findings that reliance on a traditional landline telephone sampling approach effectively excludes distinct subgroups of the population from being represented inresearch findings. Consequently, we suggest that research best practice necessitates the use of a dual- rame sampling methodology. Despite inherent logistical and cost issues, this approach  needs to become the norm in gambling survey research.

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Despite growing popularity of experience sampling methodology (ESM) for evaluations of state-based components of body image, there have been concerns that the frequent repeated measurement might encourage problematic responding resulting in low data quantity and/or quality. Using a sample of 105 women (mean age = 24.84), this study used multilevel modelling to investigate whether (a) there were changes in compliance or response variability across a 7-day period, and (b) whether such changes are explained by participant characteristics. Present findings suggest that demands of ESM protocol undermine quantity more so than quality of obtained data. Decline in procedural compliance across the testing period correlated with BMI and body shame, whereas reduced variability in state-based assessments did not adversely impact the strength of association between state body satisfaction ratings and other variables in the dataset. The authors make several recommendations for ensuring the quality of ESM-based data in future studies.

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At-sea distributions of large scyphozoan jellyfish across the Irish Sea were studied using visual surface counts from ships of opportunity. Thirty-seven surveys were conducted along two >100 km long transects between Ireland and the UK from April to September in 2009 and 2010. Five species were recorded but only Aurelia aurita and Cyanea capillata were frequently observed. The first formal description of the seasonal changes in the abundances and distributions of these two species in the study area is provided. The highest densities of these species were more likely to be found ~30 km offshore, but large aggregations were present both in coastal and offshore waters. Evidence for aggregations of medusae along physical discontinuities was provided by coupling jellyfish observations with simultaneous records of environmental parameters. The value of surveys from ships of opportunity as cost-effective semi-quantitative tools, to develop local knowledge on jellyfish abundance, distribution, and phenology is discussed.

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In species of conservation concern it is often difficult to be certain that population diversity and structure have been adequately characterised by genetic sampling. Since practical and financial constraints tend to be associated with increasing sample sizes in many conservation genetic studies, it is important to consider the potential for sampling error and bias due to inadequate samples or spatio-temporal structure within populations. We analysed sequence data from the mitochondrial DNA control region in a large sample (n = 245) of green sea turtles Chelonia mydas collected at the globally important rookery of Ascension Island, South Atlantic. We examined genetic diversity and structure among 10 sampling sites, 4 beach clusters and 4 nesting seasons, and evaluated the genetic composition of Ascension against other Atlantic nesting populations, including the well-studied rookery at Tortuguero (Costa Rica). Finally, we used rarefaction and GENESAMP analyses to assess the ability of different sample sizes to provide acceptable genetic representations of a population, using Ascension and Tortuguero as models. On Ascension, we found 13 haplotypes, of which only 3 had been previously observed in the rookery, and 5 previously undescribed. We detected no differentiation among beach clusters or sampling seasons, and only weak differentiation among the 3 primary nesting sites. The increased sample size for Ascension provided higher resolution and statistical power in describing genetic structure among all other known Atlantic rookeries. Our extrapolations showed that a maximum of 18 and 6 haplotypes are expected to occur in Ascension and Tortuguero, respectively, and that current sample sizes are sufficient to describe most of the variation. We recommend using rarefaction and GENESAMP analyses on a rookery-by-rookery basis to evaluate whether a sample set adequately describes mitochondrial DNA diversity, thus strengthening subsequent phylogeographic and mixed stock analyses, and management recommendations for conservation.

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To date, there has been limited empirical scrutiny of the correlates and consequences of day-to-day state body dissatisfaction fluctuations within naturalistic contexts. We used ecological momentary assessment (a form of naturalistic observation) to evaluate whether state body dissatisfaction was concurrently and/or prospectively associated with occurrence and quality of social interactions. Women (N = 121), aged 18 to 40, completed a brief trait-based survey and then nominated a 7-day period within which to receive seven text messages daily, at random intervals, prompting them to complete measures of body dissatisfaction at that moment. If they were currently or had recently engaged in social interactions, they were also asked to fill out questions rating the quality of these interactions (operationalized in terms of enjoyment of, and control in, the interaction). Findings suggest that the relationship between state body dissatisfaction and aspects of social interactions is complex and may vary over time. Cross-sectionally, state body dissatisfaction and social interaction quality were negatively associated. Prospectively, however, body dissatisfaction predicted subsequent avoidance of social interactions. Interestingly, when women chose to avoid social interactions, their body dissatisfaction worsened, yet when they did engage in social interactions, they reported improved body satisfaction. Importantly, the links between state body dissatisfaction and social interactions may be moderated by body mass index and trait body satisfaction levels. Potential mechanisms underlying the association between state body dissatisfaction and quality and quantity of social interactions are discussed, and future research avenues are proposed to further understand their inter-relation.

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Informed decisions about sampling are critical to improving the quality of research synthesis. Even though several qualitative research synthesists have recommended purposeful sampling for synthesizing qualitative research, the published literature holds sparse discussion on how different strategies for purposeful sampling may be applied to a research synthesis. In primary research, Patton is frequently cited as an authority on the topic of purposeful sampling. In Patton’s original texts that are referred to in this article, Patton does not make any suggestion of using purposeful sampling for research synthesis. This article makes a unique contribution to the literature by examining the adaptability of each of Patton’s 16 purposeful sampling strategies to the process of qualitative research synthesis. It illuminates how different purposeful sampling strategies might be particularly suited to constructing multi-perspectival, emancipatory, participatory and deconstructive interpretations of published research.