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18-467: The German Socio-Economic Panel (SOEP [ /'zœp/ ], for Sozio-oekonomisches Panel ) is a longitudinal panel dataset of the population in Germany. It is a household based study which started in 1984 and which reinterviews adult household members annually. Additional samples have been taken from time to time. In 2015, there will be about 14,000 households, and more than 30,000 adult persons sampled. Some of

36-418: A common event. As opposed to observing an entire population, a panel study follows a smaller, selected group - called a 'panel'. When longitudinal studies are observational , in the sense that they observe the state of the world without manipulating it, it has been argued that they may have less power to detect causal relationships than experiments . Others say that because of the repeated observation at

54-500: Is about the possible effect of a treatment on subjects, where the assignment of subjects into a treated group versus a control group is outside the control of the investigator. This is in contrast with experiments , such as randomized controlled trials , where each subject is randomly assigned to a treated group or a control group. Observational studies, for lacking an assignment mechanism, naturally present difficulties for inferential analysis. The independent variable may be beyond

72-1091: Is available online. SOEP data are integrated into the Cross National Equivalent File (CNEF) which contains panel data from Australia, Canada, Germany, Great Britain and the United States. The data distribution of the SOEP for researchers outside Germany is supplied with the CNEF by a group at Ohio State University . Application to use this international distribution has to be made to the DIW Berlin . 52°30′44″N 13°23′19.32″E  /  52.51222°N 13.3887000°E  / 52.51222; 13.3887000 Longitudinal study Longitudinal studies are often used in social-personality and clinical psychology , to study rapid fluctuations in behaviors, thoughts, and emotions from moment to moment or day to day; in developmental psychology , to study developmental trends across

90-521: Is used by both researchers and policymakers to better understand how Australians are aging and using health services to prevent and manage ill-health and disability and guide health system decisions. 45 and Up is the largest ongoing study of healthy aging in the Southern Hemisphere. GUiNZ is New Zealand's largest ongoing longitudinal study. It follows approximately 11% of all NZ children born between 2009 and 2010. The study aims to look in depth at

108-515: The approximation of experimental control with statistical control by using matching methods. Matching methods account for the influences of observed factors that might influence a cause-and-effect relationship. In healthcare and the social sciences , investigators may use matching to compare units that nonrandomly received the treatment and control. One common approach is to use propensity score matching in order to reduce confounding , although this has recently come under criticism for exacerbating

126-428: The collection of new data). Cohort studies are one type of longitudinal study which sample a cohort (a group of people who share a defining characteristic, typically who experienced a common event in a selected period, such as birth or graduation) and perform cross-section observations at intervals through time. Not all longitudinal studies are cohort studies; some instead include a group of people who do not share

144-399: The control of the investigator for a variety of reasons: "Although observational studies cannot be used to make definitive statements of fact about the "safety, efficacy, or effectiveness" of a practice, they can: In all of those cases, if a randomized experiment cannot be carried out, the alternative line of investigation suffers from the problem that the decision of which subjects receive

162-531: The goal is to determine the effects of the factors. Sometimes the recorded factors may not be directly causing the differences in the output. There may be more important factors which were not recorded but are, in fact, causal. Also, recorded or unrecorded factors may be correlated which may yield incorrect conclusions. Another difficulty with observational studies is that researchers may themselves be biased in their observational skills. This would allow for researchers to (either consciously or unconsciously) seek out

180-476: The health and well-being of children (and their parents) growing up in NZ. Observational study In fields such as epidemiology , social sciences , psychology and statistics , an observational study draws inferences from a sample to a population where the independent variable is not under the control of the researcher because of ethical concerns or logistical constraints. One common observational study

198-657: The individual level, they have more power than cross-sectional observational studies, by virtue of being able to exclude time-invariant unobserved individual differences and also of observing the temporal order of events. Longitudinal studies do not require large numbers of participants (as in the examples below). Qualitative longitudinal studies may include only a handful of participants, and longitudinal pilot or feasibility studies often have fewer than 100 participants. Longitudinal studies are time-consuming and expensive. Longitudinal studies cannot avoid an attrition effect: that is, some subjects cannot continue to participate in

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216-422: The life span; and in sociology , to study life events throughout lifetimes or generations; and in consumer research and political polling to study consumer trends. The reason for this is that, unlike cross-sectional studies , in which different individuals with the same characteristics are compared, longitudinal studies track the same people, and so the differences observed in those people are less likely to be

234-1000: The many topics surveyed include household composition, occupation, employment, earnings, health and life satisfaction . The annual surveys are conducted by the German Institute for Economic Research (DIW Berlin) and the Kantar Group . The survey is funded by the German Federal Government and the State of Berlin via the «Bund-Länder-Kommission» (State/Federal State Commission) for Educational Planning and Research Promotion. Data are available to social science researchers in Germany and abroad in SPSS / PSPP , SAS / DAP , Stata , R / S-PLUS and ASCII format. Extensive documentation in English and German

252-399: The result of cultural differences across generations, that is, the cohort effect . Longitudinal studies thus make observing changes more accurate and are applied in various other fields. In medicine, the design is used to uncover predictors of certain diseases. In advertising, the design is used to identify the changes that advertising has produced in the attitudes and behaviors of those within

270-411: The study for various reasons. Under longitudinal research methods, the reduction in the research sample will bias the remaining smaller sample. Practice effect is also one of the problems: longitudinal studies tend to be influenced because subjects repeat the same procedure many times (potentially introducing autocorrelation ), and this may cause their performance to improve or deteriorate. The Study

288-512: The target audience who have seen the advertising campaign. Longitudinal studies allow social scientists to distinguish short from long-term phenomena, such as poverty . If the poverty rate is 10% at a point in time, this may mean that 10% of the population are always poor or that the whole population experiences poverty for 10% of the time. Longitudinal studies can be retrospective (looking back in time, thus using existing data such as medical records or claims database) or prospective (requiring

306-449: The treatment is not entirely random and thus is a potential source of bias . A major challenge in conducting observational studies is to draw inferences that are acceptably free from influences by overt biases, as well as to assess the influence of potential hidden biases. The following are a non-exhaustive set of problems especially common in observational studies. In lieu of experimental control, multivariate statistical techniques allow

324-411: The very problems it seeks to solve. Multiple comparison bias can occur when several hypotheses are tested at the same time. As the number of recorded factors increases, the likelihood increases that at least one of the recorded factors will be highly correlated with the data output simply by chance. An observer of an uncontrolled experiment (or process) records potential factors and the data output:

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