982 resultados para survey sampling
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Introduction The European Foundation for the improvement of living and working conditions conducts a survey every 5 years since 1990. The foundation also offers the possibility to non-EU countries to be included in the survey: in 2005, Switzerland took part for the first time in the fourth edition of this survey. The Institute for Work and Health (IST) has been associated to the Swiss project conducted under the leadership of the SECO and the Fachhochschule Nordwestschweiz. The survey covers different aspects of work like job characteristics and employment conditions, health and safety, work organization, learning and development opportunities, and the balance between working and non-working life (Parent-Thirion, Fernandez Macias, Hurley, & Vermeylen, 2007). More particularly, one question assesses the worker's self-perception of the effects of work on health. We identified (for the Swiss sample) several factors affecting the risk to report health problems caused by work. The Swiss sample includes 1040 respondents. Selection of participants was based on a random multi-stage sampling and was carried out by M.I.S Trend S.A. (Lausanne). Participation rate was 59%. The database was weighted by household size, gender, age, region of domicile, occupational group, and economic sector. Specially trained interviewers carried out the interviews at the respondents home. The survey was carriedout between the 19th of September 2005 and the 30th of November 2005. As detailed in (Graf et al., 2007), 31% of the Swiss respondents identify work as the cause of health problems they experience. Most frequently reported health problems include back pain (18%), stress (17%), muscle pain (13%), and overall fatigue (11%). Ergonomic aspects associated with higher risk of reporting health problems caused by work include frequent awkward postures (odds ratio [OR] 4.7, 95% confidence interval [CI] 3.1 to 5.4), tasks involving lifting heavy loads (OR 2.7, 95% CI 2.0 to 3.6) or lifting people (OR 2.2, 95% CI 1.4 to 3.5), standing or walking (OR 1.4, 95% CI 1.1 to 1.9), as well as repetitive movements (OR 1.7, 95% CI 1.3 to 2.3). These results highlight the need to continue and intensify the prevention of work related health problems in occupations characterized by risk factors related to ergonomics.
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Survey of potential sharpshooter and spittlebug vectors of Xylella fastidiosa to grapevines at the São Francisco River Valley, Brazil. Pierce's disease of grapevines, caused by Xylella fastidiosa, is a serious problem in some regions of North America, not yet reported in Brazil. In this study, a survey of potential sharpshooter (Hemiptera, Cicadellidae, Cicadellinae) and spittlebug (Hemiptera, Cercopidae) vectors of X. fastidiosa was conducted in vineyards at the São Francisco River Valley, a major grape growing region in Brazil. Four vineyards of Vitis vinifera L. were sampled fortnightly from June/2005 to June/2007, using yellow sticky cards, each placed at two different heights (45 cm aboveground and 45 cm above the crop canopy) in 10 sampling localities. A total of 4,095 specimens of sharpshooters were collected, nearly all from 3 Proconiini species, Homalodisca spottii Takiya, Cavichioli & McKamey, 2006 (96.8% of the specimens), Tapajosa fulvopunctata (Signoret, 1854) (3.1%), and Tretogonia cribrata Melichar, 1926 (1 specimen). Hortensia similis (Walker, 1851) (2 specimens) was the only Cicadellini species. Only 1 cercopid specimen, belonging to Aeneolamia colon (Germar, 1821), was trapped. Even though they are not considered potential Xylella vectors, 2 Gyponini leafhoppers were collected: Curtara samera DeLong & Freytag, 1972 (11 specimens) and Curtara inflata DeLong & Freytag, 1976 (1 specimen). Homalodisca spottii was observed feeding and mating on green branches of grapevines, in addition to egg masses. Because of its prevalence on the crop canopy, occurrence throughout the year (with peaks from February to August), and ability to colonize grapevines, H. spottii could be an important vector if a X. fastidiosa strain pathogenic to grapevines becomes introduced at the São Francisco River Valley.
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OBJECTIVES: To conduct a national survey on adolescent health and lifestyles in Georgia and to thus set up a database on adolescent. METHODS: A two-stage cluster sample of around 8000-10000 in-school 15-18 years adolescents are being reached through a random selection of classes in Georgia. The sample has been stratified by age, region, type of school and language. A self-administered questionnaire of 87 questions has been developed and translated into the four main languages used in Georgia. RESULTS: Up to June 2004, the researchers have reached 511 classes (9306 pupils). In total, 8039 questionnaires have been considered valid. The main concerns encountered for this survey are linked with acceptance of the survey, cross-cultural issues, political and strategic problems as well as inadequate physical environmental support. CONCLUSION: Despite Georgia's unfavourable economical and political situation, it has been possible to run a national survey on the health of adolescents, according to the usual standards used in the field. This survey should allow for 1) the identification of priorities in the field of health care and health promotion 2) the monitoring of adolescent health in the future.
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The pursuit of high response rates to minimise the threat of nonresponse bias continues to dominate decisions about resource allocation in survey research. Yet a growing body of research has begun to question this practice. In this study, we use previously unavailable data from a new sampling frame based on population registers to assess the value of different methods designed to increase response rates on the European Social Survey in Switzerland. Using sampling data provides information about both respondents and nonrespondents, making it possible to examine how changes in response rates resulting from the use of different fieldwork methods relate to changes in the composition and representativeness of the responding sample. We compute an R-indicator to assess representativity with respect to the sampling register variables, and find little improvement in the sample composition as response rates increase. We then examine the impact of response rate increases on the risk of nonresponse bias based on Maximal Absolute Bias (MAB), and coefficients of variation between subgroup response rates, alongside the associated costs of different types of fieldwork effort. The results show that increases in response rate help to reduce MAB, while only small but important improvements to sample representativity are gained by varying the type of effort. These findings lend further support to research that has called into question the value of extensive investment in procedures aimed at reaching response rate targets and the need for more tailored fieldwork strategies aimed both at reducing survey costs and minimising the risk of bias.
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Identifying the geographic distribution of populations is a basic, yet crucial step in many fundamental and applied ecological projects, as it provides key information on which many subsequent analyses depend. However, this task is often costly and time consuming, especially where rare species are concerned and where most sampling designs generally prove inefficient. At the same time, rare species are those for which distribution data are most needed for their conservation to be effective. To enhance fieldwork sampling, model-based sampling (MBS) uses predictions from species distribution models: when looking for the species in areas of high habitat suitability, chances should be higher to find them. We thoroughly tested the efficiency of MBS by conducting an important survey in the Swiss Alps, assessing the detection rate of three rare and five common plant species. For each species, habitat suitability maps were produced following an ensemble modeling framework combining two spatial resolutions and two modeling techniques. We tested the efficiency of MBS and the accuracy of our models by sampling 240 sites in the field (30 sitesx8 species). Across all species, the MBS approach proved to be effective. In particular, the MBS design strictly led to the discovery of six sites of presence of one rare plant, increasing chances to find this species from 0 to 50%. For common species, MBS doubled the new population discovery rates as compared to random sampling. Habitat suitability maps coming from the combination of four individual modeling methods predicted well the species' distribution and more accurately than the individual models. As a conclusion, using MBS for fieldwork could efficiently help in increasing our knowledge of rare species distribution. More generally, we recommend using habitat suitability models to support conservation plans.
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Iowa’s traffic safety culture is influenced by laws and policies, enforcement methods, driver education, roadway engineering, and drivers’ behaviors. The Center for Social and Behavioral Research at the University of Northern Iowa was contracted by the Iowa Department of Transportation to conduct a general population survey of adult Iowans. Telephone interviews were conducted with 1,088 adult Iowans from October to December 2011. A dual-frame (cell phone and landline) sampling design was used. The interview covered a wide range of traffic safety topics (e.g., traffic safety policies, enforcement techniques, and distracted driving). Most Iowans said driving in Iowa is about as safe now as it was 5 years ago; however, one-fourth said driving in Iowa is less safe now. There are a number of driving-related behaviors many adult Iowans consider serious threats to traffic safety and never acceptable to do while driving. Yet, many Iowans report often seeing other drivers engaging in these behaviors and admit engaging in some themselves. For example, nearly 1 in 5 adult Iowa drivers said they have sent or read a text message or email while driving in the past 30 days despite this being prohibited since July of 2011. A slight majority said they support using cameras on highways, interstates, and city streets to automatically ticket drivers for speeding, with even stronger support for red light cameras. A comprehensive approach to traffic safety in Iowa is required to encourage protective factors that enhance traffic safety and reduce the impact of detrimental factors.
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Because data on rare species usually are sparse, it is important to have efficient ways to sample additional data. Traditional sampling approaches are of limited value for rare species because a very large proportion of randomly chosen sampling sites are unlikely to shelter the species. For these species, spatial predictions from niche-based distribution models can be used to stratify the sampling and increase sampling efficiency. New data sampled are then used to improve the initial model. Applying this approach repeatedly is an adaptive process that may allow increasing the number of new occurrences found. We illustrate the approach with a case study of a rare and endangered plant species in Switzerland and a simulation experiment. Our field survey confirmed that the method helps in the discovery of new populations of the target species in remote areas where the predicted habitat suitability is high. In our simulations the model-based approach provided a significant improvement (by a factor of 1.8 to 4 times, depending on the measure) over simple random sampling. In terms of cost this approach may save up to 70% of the time spent in the field.
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Autopsy-negative sudden cardiac deaths (SCD) seen in forensic practice are most often thought to be the result of sudden arrhythmic death syndrome. Postmortem genetic analysis is recommended in such cases, but is currently performed in only a few academic centers. In order to determine actual current practice, an on-line questionnaire was sent by e-mail to members of various forensic medical associations. The questions addressed routine procedures employed in cases of sudden cardiac death (autopsy ordering, macroscopic and microscopic cardiac examination, conduction tissue examination, immunohistochemistry and electron microscopy, biochemical markers, sampling and storage of material for genetic analyses, toxicological analyses, and molecular autopsy). Some questions concerned the legal and ethical aspects of genetic analyses in postmortem examinations, as well as any existing multidisciplinary collaborations in SCD cases. There were 97 respondents, mostly from European countries. Genetic testing in cases of sudden cardiac death is rarely practiced in routine forensic investigation. Approximately 60% of respondents reported not having the means to perform genetic postmortem testing and 40% do not collect adequate material to perform these investigations at a later date, despite working at university hospitals. The survey demonstrated that many of the problems involved in the adequate investigation of SCD cases are often financial in origin, due to the fact that activities in forensic medicine are often paid by and dependent on the judicial authorities. Problems also exist concerning the contact with family members and/or the family doctor, as well as the often-nonexistent collaboration with others clinicians with special expertise beneficial in the investigation of SCD cases, such as cardiologists and geneticists. This study highlights the importance in establishing guidelines for molecular autopsies in forensic medicine.
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The objective of this study was to evaluate the diversity of fruit fly (Diptera: Tephritidae) species that use myrtaceous fruit, particularly guava, as hosts in several localities in the state of Bahia and to determine the infestation rates, pupal viability rates, and fruit fly-parasitoid associations. Sampling of myrtaceous fruit was carried out in 24 municipalities in different regions in the state of Bahia. Four fruit fly species, Anastrepha fraterculus, Anastrepha zenildae, Anastrepha sororcula, and Ceratitis capitata were obtained from the collected fruit. Three parasitoid species (Hymenoptera: Braconidae) emerged from Anastrepha larvae/pupae, Doryctobracon areolatus, Utetes anastrephae, and Asobara anastrephae. Doryctobracon areolatus emerged from A. fraterculus, A. sororcula and A. zenildae; Utetes anastrephae emerged from A. fraterculus and A. zenildae; and Asobara anastrephae emerged from A. fraterculus. Fruit fly and myrtaceous fruit associations are reported for the first time in several municipalities in the state of Bahia. A. zenildae was found infesting Syzygium malaccense for the first time in Brazil.
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For landline telephone surveys in particular, undercoverage has been a growing problem. However, research regarding the relative contributions of socio-demographic bias and other composition effects is scarce. We propose to address this issue by analyzing an election survey which used a sample from a register-based sampling frame containing basic socio-demographic information and to which telephone numbers were subsequently matched. With respect to socio-demographic representation of the final sample, we find that difficult to match groups are also difficult to contact, while those who cooperate tend to have different characteristics. We find bias due to undercoverage to be of greater magnitude than noncontact bias, while noncooperation falls between the two. As for substantive variables, both additional efforts to match missing telephone numbers and the construction of better weights are successful in closing the gap between survey estimates of voting behavior and true values from the election results.
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Longitudinal surveys are increasingly used to collect event history data on person-specific processes such as transitions between labour market states. Surveybased event history data pose a number of challenges for statistical analysis. These challenges include survey errors due to sampling, non-response, attrition and measurement. This study deals with non-response, attrition and measurement errors in event history data and the bias caused by them in event history analysis. The study also discusses some choices faced by a researcher using longitudinal survey data for event history analysis and demonstrates their effects. These choices include, whether a design-based or a model-based approach is taken, which subset of data to use and, if a design-based approach is taken, which weights to use. The study takes advantage of the possibility to use combined longitudinal survey register data. The Finnish subset of European Community Household Panel (FI ECHP) survey for waves 1–5 were linked at person-level with longitudinal register data. Unemployment spells were used as study variables of interest. Lastly, a simulation study was conducted in order to assess the statistical properties of the Inverse Probability of Censoring Weighting (IPCW) method in a survey data context. The study shows how combined longitudinal survey register data can be used to analyse and compare the non-response and attrition processes, test the missingness mechanism type and estimate the size of bias due to non-response and attrition. In our empirical analysis, initial non-response turned out to be a more important source of bias than attrition. Reported unemployment spells were subject to seam effects, omissions, and, to a lesser extent, overreporting. The use of proxy interviews tended to cause spell omissions. An often-ignored phenomenon classification error in reported spell outcomes, was also found in the data. Neither the Missing At Random (MAR) assumption about non-response and attrition mechanisms, nor the classical assumptions about measurement errors, turned out to be valid. Both measurement errors in spell durations and spell outcomes were found to cause bias in estimates from event history models. Low measurement accuracy affected the estimates of baseline hazard most. The design-based estimates based on data from respondents to all waves of interest and weighted by the last wave weights displayed the largest bias. Using all the available data, including the spells by attriters until the time of attrition, helped to reduce attrition bias. Lastly, the simulation study showed that the IPCW correction to design weights reduces bias due to dependent censoring in design-based Kaplan-Meier and Cox proportional hazard model estimators. The study discusses implications of the results for survey organisations collecting event history data, researchers using surveys for event history analysis, and researchers who develop methods to correct for non-sampling biases in event history data.
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The use of the Roundup Ready(r) technology and the cultivation of a second crop influence the floristic composition of weed communities in Brazilian Central-West region cropping systems. This study has aimed to diagnose the dominant weed species in southwestern Goiás in areas of genetically-modified and conventional soybeans, using phytosociological and floristic surveys. Weed sampling was obtained by collecting all the plants present within a 0.5 m hollow frame, randomly thrown 20 times in each of thirty-five agricultural areas in the 2012/2013 harvest. Field survey was carried out in three periods: before desiccation for soybean sowing, before postemergence herbicide in soybean first application and before postemergence herbicide application in late harvest. A total of 525 m2 was inventoried and 3,219 weeds were collected, which included 79 species, 58 genera and 28 families. Families Poaceae, Asteraceae, Euphorbiaceae, Fabaceae, Amaranthaceae, were the most representative in the survey. Species Cenchrus echinatus, Glycine max, Chamaesyce hirta, Commelina benghalensis, and Alternanthera tenella stood out in importance. The RR+millet soybean treatment had the highest number of species (44), while the conventional soybean + sorghum treatment had the lowest number of species (18). The highest number of species was recorded in first sampling period. Treatments conventional soybean + maize and conventional soybean + millet showed higher similarity (70%), while treatments RR soybean + millet and conventional soybean + sorghum showed the least (51%). Species of difficult control were recorded in all cultivation systems analyzed.
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The purpose of this cross sectional survey design was to examine self-reported health status and lifestyle behaviours of the residents of the Town of Fort Erie, Ontario, as related to the Canadian Community Health Survey. Using a mail-out survey, entitled the Fort Erie Survey of Health (FESH), a probability cluster sampling technique was used to measure self-reported health status (present health, health conditions, health challenges, functional health limitations) and lifestyle behaviour (smoking, alcohol use, drug use, physical activity, fruit and vegetable consumption, body weight, and gaming). Each variable was described and analyzed in relation to socio-economic variables, age and gender. The findings from this study were compared to the Canadian Community Health Survey 2000/2001. Overall, 640 surveys were completed. The majority of Fort Erie residents rated their present health as good and were satisfied with their overall health and quality of life. The main chronic conditions reported were arthritis, back pain and heart disease. Other main health problems reported were vision, sleeping and chronic pain. Overall, 14.6% smoke; 58.8% engaged in physical activity either occasionally or never as opposed to regularly engaging in physical activity; 52.1% did not eat the required daily fruits and vegetables; and 40.0% were in the overweight category. Persons who practiced one healthy lifestyle behaviour were more likely to practice other healthy promoting behaviours. Therefore, health promotion programs are best designed to address multiple risk factors simultaneously. The ffiSH was generally consistent with the Canadian Community Health Survey in the overall findings. A small number of inconsistencies were identified that require further exploration to determine if they are unique to this community.
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Background: An important challenge in conducting social research of specific relevance to harm reduction programs is locating hidden populations of consumers of substances like cannabis who typically report few adverse or unwanted consequences of their use. Much of the deviant, pathologized perception of drug users is historically derived from, and empirically supported, by a research emphasis on gaining ready access to users in drug treatment or in prison populations with higher incidence of problems of dependence and misuse. Because they are less visible, responsible recreational users of illicit drugs have been more difficult to study. Methods: This article investigates Respondent Driven Sampling (RDS) as a method of recruiting experienced marijuana users representative of users in the general population. Based on sampling conducted in a multi-city study (Halifax, Montreal, Toronto, and Vancouver), and compared to samples gathered using other research methods, we assess the strengths and weaknesses of RDS recruitment as a means of gaining access to illicit substance users who experience few harmful consequences of their use. Demographic characteristics of the sample in Toronto are compared with those of users in a recent household survey and a pilot study of Toronto where the latter utilized nonrandom self-selection of respondents. Results: A modified approach to RDS was necessary to attain the target sample size in all four cities (i.e., 40 'users' from each site). The final sample in Toronto was largely similar, however, to marijuana users in a random household survey that was carried out in the same city. Whereas well-educated, married, whites and females in the survey were all somewhat overrepresented, the two samples, overall, were more alike than different with respect to economic status and employment. Furthermore, comparison with a self-selected sample suggests that (even modified) RDS recruitment is a cost-effective way of gathering respondents who are more representative of users in the general population than nonrandom methods of recruitment ordinarily produce. Conclusions: Research on marijuana use, and other forms of drug use hidden in the general population of adults, is important for informing and extending harm reduction beyond its current emphasis on 'at-risk' populations. Expanding harm reduction in a normalizing context, through innovative research on users often overlooked, further challenges assumptions about reducing harm through prohibition of drug use and urges consideration of alternative policies such as decriminalization and legal regulation.
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Roadside surveys such as the Breeding Bird Survey (BBS) are widely used to assess the relative abundance of bird populations. The accuracy of roadside surveys depends on the extent to which surveys from roads represent the entire region under study. We quantified roadside land cover sampling bias in Tennessee, USA, by comparing land cover proportions near roads to proportions of the surrounding region. Roadside surveys gave a biased estimate of patterns across the region because some land cover types were over- or underrepresented near roads. These biases changed over time, introducing varying levels of distortion into the data. We constructed simulated population trends for five bird species of management interest based on these measured roadside sampling biases and on field data on bird abundance. These simulations indicated that roadside surveys may give overly negative assessments of the population trends of early successional birds and of synanthropic birds, but not of late-successional birds. Because roadside surveys are the primary source of avian population trend information in North America, we conclude that these surveys should be corrected for roadside land cover sampling bias. In addition, current recommendations about the need to create more early successional habitat for birds may need reassessment in the light of the undersampling of this habitat by roads.