In statistics , samplingbias is when a sample is collected in such a way that some members of the intended ... Dictionary SamplingBias Retrieved on September 23, 2009 ref of a statistical population population ... than to the method of sampling statistics sampling . Medical sources sometimes refer to samplingbias as ascertainment bias . ref cite book author Weising, Kurt title DNA fingerprinting in plants principles ... selection biasSamplingbias is mostly classified as a subtype of selection , ref http medical.webends.com kw Selection 20Bias Dictionary of Cancer Terms Selection Bias Retrieved on September 23, 2009 ref sometimes specifically termed sample selection bias , ref http www.ncbi.nlm.nih.gov pubmed 9504213 The effects of sample selection bias on racial differences in child abuse reporting Ards S, Chung ... accepted, of samplingbias is that it undermines the external validity of a test the ability of its ... occurring in the process of gathering the sample or cohort cause samplingbias, while errors in any process thereafter cause selection bias. However, selection bias and samplingbias are often used ... Types of samplingbias Selection from a specific real area . For example, a survey of high school ... bias.png 600px center thumbnail Simple pedigree example of samplingbias Geneticists are limited ... lived in caves for most of their lives. Problems caused by samplingbias A biased sample causes ... selected. ref http medical dictionary.thefreedictionary.com Sample bias TheFreeDictionary biased sample ... bias Francesc Calafell i Maj , Anna Ram rez i Soriano. July 2008 ref Ascertainment bias has basically ... Medical Dictionary Ascertainment Bias Retrieved on November 14, 2009 ref but is still sometimes classified as a separate type of bias. ref name saem http www.saem.org SAEMDNN Portals 0 AnnualMeeting09 ... ref http www.cs.nyu.edu mohri postscript bias.pdf Sample Selection Bias Correction Theory Corinna ... it as a separate type of bias. ref http books.google.com books?id f0IDHvLiWqUC&printsec frontcover&source ... more details
wiktionarypar samplingSampling may refer to Sampling signal processing , converting a continuous signal into a discrete signal Sample graphics Sampling graphics , converting continuous colors into discrete color components Sampling music , re using portions of sound recordings in a piece Sampler musical instrument , an electronic music instrument that plays back sound recordings on command Sampling statistics , selection of observations to acquire some knowledge of a statistical population Sampling case studies , selection of cases for single or multiple case studies Sampling audit , application of audit procedures to less than 100 of population to be audited Sampling medicine , gathering of matter from the body to aid in the process of a medical diagnosis and or evaluation of an indication for treatment, further medical tests or other procedures. Sampling for testing or analysis , taking a representative portion of a material or product to test e.g. by physical measurements, chemical analysis, microbiological examination , typically for the purposes of identification, quality control, or regulatory assessment Specific types of sampling include Chorionic villus sampling , a method of detecting fetal abnormalities Food sampling , the process of taking a representative portion of a food ... with free sample Food, free samples , a method of promoting food items to consumers Oil sampling , the process of collecting samples of oil from machinery for analysis Theoretical sampling , the process of selecting comparison cases or sites in qualitative research Water sampling , the process of taking ... sampling , a method of estimating the standard time for manufacturing operations. See also Sample disambiguation Sampler disambiguation disambig ca Mostreig cs Vzorkov n rozcestn k de Sampling es Muestreo fa fr chantillonnage ko it Campionamento he ja no Sampling pl Sampling pt Amostragem ru simple Sampling sv Sampling ... more details
other uses2 Bias advert date November 2011 Infobox company company name BIAS company logo Image Biaslogo.png ... Software industry Technology homepage http www.bias inc.com www.bias inc.com BIAS originally known ... used in his musical compositions. Peak started out as a utility for transferring content Sampling music ..., BIAS Peak Peak , which remains as BIAS flagship product to this day. BIAS Inc. was founded in 1994 in Sausalito, California, by Steve and Christine Berkley. Products Peak BIAS Peak Peak is a full featured professional stereo sample editor and BIAS flagship product. Peak s approach to editing differs ... Express . Peak runs on Mac OS X computer systems. SoundSoap BIAS SoundSoap SoundSoap is a noise reduction ... OS X and Windows XP computer systems. SoundSoap Pro BIAS SoundSoap SoundSoap Pro is a professional ... systems. Product timeline 1 96 Peak 1.0 debuts at NAMM Show in Anaheim, CA. br 11 96 BIAS Introduces ... br 9 98 BIAS acquires Deck DAW from Macromedia br 12 98 Peak 2.0 introduced adds Digital audio editor ... 2011 plug in support, and CD burning br 8 99 BIAS Brings Peak to BeOS br 1 00 Peak 2.1 adds Audio Stream ... with third party audio hardware br 1 01 BIAS introduces Deck LE entry level DAW br 7 01 BIAS ... and Peak LE 3.0 introduced run on Mac OS 8.6, 9.x, X br 1 02 BIAS introduces SuperFreq paragraphic equalizer plug in for Mac OS 8.6, 9.x, X br 6 02 BIAS introduces Deck 3.5 the first professional DAW to run on Mac OS X adds 5.1 surround mixing br 7 02 Entire BIAS product line now runs on Mac OS X br 8 02 BIAS introduces Vbox 1.1 runs on Mac OS X and Windows operating systems br 12 02 BIAS introduces ... br 8 05 BIAS introduces Peak Pro 5 adds industry leading sample rate conversion and graphical waveform view to playlist, Disc Description Protocol DDP export capability br 9 05 BIAS introduces Peak ... runs natively on PPC and Intel based Macintosh computers External links http www.bias inc.com BIAS website http www.bias inc.com forums BIAS User Discussion Forum DEFAULTSORT Bias Category Software ... more details
about different ways the term bias is used Bias is an inclination to present or hold a partial perspective at the expense of possibly equally valid alternatives. Bias can come in many forms In statistics main Bias statistics In judgment and decision making main Cognitive bias A cognitive bias is the human tendency to make systematic decisions in certain circumstances based on cognitive factors rather than evidence. Bias arises from various processes that are sometimes difficult to distinguish. These processes include information processing shortcuts, motivational factors, and social influence Wilcox, 2011 . Such biases can result from information processing shortcuts called heuristics . They include errors in judgment, social attribution , and memory. Cognitive biases are a common outcome of human ... main Media bias Media bias is the bias of journalist s and news producer s within the mass ... media bias implies a pervasive or widespread bias contravening Journalism ethics and standards the standards ... and degree of media bias in various countries is widely disputed. Practical limitations to media ... bias has been a feature of the mass media since its birth with the invention of the printing ... a law contract in their favor for economic reasons. Inductive bias in machine learning. Cultural bias interpreting and judging phenomena in terms particular to one s own culture. Racism , regionalism ... by willfull bias, assumption or, putting conclusion ahead of evidence. In practice .... Funding bias in scientific studies also known as the agent principle dilemma . Medical bias is also ... 24 2893 289. ref Biasing or bias in electrical engineering force applied as a reference level in order ... Scholarly method Source criticism Weasel word Detection theory Experimenter s bias Social desirability bias Political correctness References reflist Wilcox, C. W. 2011 Bias The Unconscious Deceiver. Bloomington, IN Xlibris Corporation External links Wikiquote Wiktionary Biases Category Bias fa ... more details
one source date February 2012 During sampling of Particulate matter particulate materials , correct sampling is defined in Gy s sampling theory as a sampling scenario in which all particles in a population have the same probability of ending up in the sample. ref name Gy1979 P. M. Gy 1979 , Sampling of Particulate Materials theory and practice. Elsevier Amsterdam, 431 pp. ref The concentration of the property of interest in a sample can be a Bias statistics biased estimate for the concentration of the property of interest in the population from which the sample is drawn. Although generally non zero, for correct sampling this bias is thought to be negligible. ref name Gy1979 See also Particulate matter sampler Statistical sampling Gy s sampling theory References Reflist Category Sampling statistics Category Particulates Category Meteorological instrumentation and equipment statistics stub ... more details
from probability based surveys may still suffer from many types of bias. Surveys that are not based on probability sampling have no way of measuring their bias or sampling error. Surveys based on non ... sampling. Bias in Probability SamplingBias in surveys is undesirable, but often unavoidable. The major types of bias that may occur in the sampling process are Non response bias When individuals or households ...In statistics , survey sampling describes the process of selecting a sample of elements from a target ... to many different types or techniques of observation, but in the context of survey sampling it most ... data collection . The purpose of sampling statistics sampling is to reduce the cost and or the amount ... sampling is often regarded a standard procedure that must be employed regardless of the cost. The Office ... e.g., probabilistic methods that can provide estimates of sampling error . Any use of nonprobability sampling methods e.g., cut off or model based samples must be justified statistically and be able ... Sampling and Inference A Prediction Approach, Wiley, New York, p. 19 ref blockquote The extreme position ... sampling In a probability sample also called scientific or random sample each member of the target ... Sampling, New York Wiley. p. 20 ref A survey based on a probability sample can in theory produce ... mean is equal to the population mean E , and ref Kish, L. 1965 , Survey Sampling, New York Wiley. p.59 ref have a measurable sampling error, which can be expressed as a confidence interval , or margin ... may be easy, for example, sampling the employees of a company by using payroll list. However, in large ... States are Area Probability Sampling, Random Digit Dial telephone sampling, and more recently Address Based Sampling. ref Michael W. Link, Michael P. Battaglia, Martin R. Frankel, Larry Osborn, and Ali H. Mokdad, A Comparison of Address Based Sampling ABS Versus Random Digit Dialing RDD for General Population Surveys Public Opinion Q, Spring 2008 72 6 27. ref Within probability sampling there are specialized ... more details
Refimprove date October 2009 sampling statistics Sampling is the use of a subset of the population statistics population to represent the whole population. Probability sampling, or random sampling , is a sampling technique in which the probability of getting any particular sample may be calculated. Nonprobability sampling does not meet this criterion and should be used with caution. Nonprobability sampling techniques cannot be used to infer from the sample to the general population. Any generalizations obtained from a nonprobability sample must be filtered through one s knowledge of the topic being studied. Performing nonprobability sampling is considerably less expensive than doing probability sampling, but the results are of limited value. Examples of nonprobability sampling include Convenience, Haphazard or Accidental sampling members of the population are chosen based on their relative ease of access. To sample friends, co workers, or shoppers at a single mall, are all examples of convenience sampling . Snowball sampling The first respondent refers a friend. The friend also refers a friend, etc. Judgmental sampling or Purposive sampling The researcher chooses the sample based on who they think would be appropriate for the study. This is used primarily when there is a limited number of people that have expertise in the area being researched. Deviant Case Get cases that substantially differ from the dominant pattern a special type of purposive sample . Case study The research ... studies due to unintentional or unavoidable characteristics of the sampling method. In public ... bias . This error sometimes makes it unlikely that the sample will accurately represent the broader ..., and the validity of the estimates of parameters based on them unknown. See also Sampling statistics Cluster sampling Judgment sample Multistage sampling Simple random sample Systematic sampling Stratified sampling DEFAULTSORT Nonprobability Sampling Category Sampling techniques Category ... more details
. Bias problems Samplingbias is a possible source of sampling errors. It leads to sampling errors ...In statistics , sampling error or estimation error is the amount of inaccuracy in estimating some value ... name Sarndal Sarndal, Swenson, and Wretman 1992 , Model Assisted Survey Sampling, Springer Verlag, ISBN 0 387 40620 4 ref Sampling error can be measured and quoted in many different ways, but in practice ... sampling In statistics , sampling error is the Errors and residuals in statistics error caused by observing a sample instead of the whole population. ref name Sarndal The sampling error can be found ... 2010 In nursing research, a sampling error is the difference between a sample statistic used to estimate ... can theoretically be expressed as sampling errors, although in practice the exact sampling error is typically unknown. Sampling error also refers more broadly to this phenomenon of random sampling variation. An example of a sampling error in evolution is genetic drift a change is a population ... represent the original population. What makes the bottleneck effect a sampling error is that certain ... it a sampling error. Another example of genetic drift that is a sampling error is the founder effect .... In this instance, there are only a few individuals with little gene variety, making it a sampling ... Benjamin Cummings pages 450 451 date year 2002 isbn ref The likely size of the sampling error can generally ... probability probabilistic estimates of the likely size of the sampling error for a particular statistic ... errors . Non sampling error Sampling error can be contrasted with non sampling error . Non sampling ... chosen, including various systematic error s and any random errors that are not due to sampling. Non sampling errors are much harder to quantify than sampling error. ref name Scheuren See also Margin of error Propagation of error Sampling statistics Citations Reflist Burns, N & Grove, S.K. ... Sampling, Springer Verlag, ISBN 0 387 40620 4 Fritz Scheuren 2005 . What is a Margin of Error? , Chapter ... more details
other uses2 Snowball More footnotes date May 2011 In sociology and statistics research, snowball sampling ref cite journal author Goodman, L.A. title Snowball sampling journal Annals of Mathematical Statistics year 1961 volume 32 issue 1 pages 148 170 doi 10.1214 aoms 1177705148 ref or chain sampling , chain referral sampling , referral sampling ref Snowball Sampling , Experiment resources.com , http www.experiment resources.com snowball sampling.html accessed 08 May 2011 . ref ref Snowball Sampling , Changing Minds.org , http changingminds.org explanations research sampling snowball sampling.htm accessed 08 May 2011 . ref is a non probability sampling technique where existing study subjects ... builds up, enough data is gathered to be useful for research. This sampling technique is often ... would be drug users or sex workers. As sample members are not selected from a sampling frame , snowball samples, analogously to Breadth first search Bias towards nodes of high degree BFS samples , ref cite conference first1 M. last1 Kurant first2 A. last2 Markopoulou first3 P. last3 Thiran. title On the bias ... first3 P. last3 Thiran. title Towards Unbiased BFS Sampling journal IEEE JSAC year 2011 volume 29 number 9 pages 1799 1809 url http arxiv.org abs 1102.4599 ref are subject to numerous Samplingbias biases . For example, people who have many friends are more likely to be recruited into the sample ..., but a variation of snowball sampling called respondent driven sampling ref cite journal first1 D.D. last1 Heckathorn title Respondent Driven Sampling A New Approach to the Study of Hidden Populations ... ref ref cite journal author Salganik, M.J. and D.D. Heckathorn title Sampling and Estimation in Hidden Populations Using Respondent Driven Sampling journal Sociological Methodology year 2004 volume 34 ... Heckathorn title Respondent Driven Sampling II Deriving Valid Estimates from Chain Referral Samples ... estimates from snowball samples under certain conditions. Snowball sampling and respondent driven ... more details
The term inherent bias refers to the effect of underlying factors or assumptions that skew viewpoints a subject under discussion. There are multiple formal definitions of inherent bias which depend on the particular field of study. In statistics , the term is used in relation to an inability to measure accuarately and directly what one would wish to measure, meaning that indirect measurements are used which might be subject to unknown distortions. See also systemic bias and systematic bias , or cognitive bias implicit assumption , paradigm shift Hawthorne effect Notes references References In opinion polls or statistics OECD Glossary of Statistical Terms Inherent bias Definition at OECD.org, April 2003, webpage http stats.oecd.org glossary detail.asp?ID 3681 Statistical Terms Inherent bias . In journalism Audeamus How dare we... The Press s Inherent Bias at Audeamus.com by Miche , September 2007, webpage http www.audeamus.com 50226711 the presss inherent bias.php The Press s Inherent Bias . Category Sampling statistics Category Polling terms Category Statistical terminology Category Bias fr Biais inh rent none yet ... more details
sampling theory may mean Nyquist Shannon sampling theorem , digital signal processing DSP Statistical sampling Fourier sampling mathdab ... more details
selecting the start between 1 and 10, this bias is eliminated. blockquote However, systematic sampling ... in the sample. The model is then built on this Samplingbias biased sample . The effects of the input ... computer simulation pseudo random number sampling In statistics and Statistical survey survey methodology , sampling is concerned with the selection of a subset of individuals from within a population ... the entire population because the cost of a census is too high. The three main advantages of sampling ... as independent objects or individuals. In survey sampling , weights can be applied to the data to adjust for the Sample statistics sample design, particularly stratified sampling Blocking statistics blocking ... and medical research, sampling is widely used for gathering information about a population. Process The sampling process comprises several stages Defining the population of concern Specifying a Sampling frame sampling frame , a Set mathematics set of items or events possible to measure Specifying a Sampling methods sampling method for selecting items or events from the frame Determining the sample size Implementing the sampling plan Sampling and data collecting Population definition Successful statistical practice is based on focused problem definition. In sampling, this includes defining ... system of which the observed population is an outcome. In such cases, sampling theory may treat ... have been overlooked at this stage. Sampling frame main Sampling frame In the most straightforward case, such as the sentencing of a batch of material from production acceptance sampling by lots , it is possible ... are not amenable to sampling in any of the ways below and to which we could apply statistical theory. As a remedy, we seek a sampling frame which has the property that we can identify every ... methodology . cite book author Lohr, Sharon L. title Sampling Design and analysis cite book author S rndal, Carl Erik, and Swensson, Bengt, and Wretman, Jan title Model Assisted Survey Sampling Scheaffer ... more details
cases, this may lead to samplingbias and in extreme cases to an unrepresentative sample . ref name S rndalSwensson2003 Such bias should be minimized, and identified, although avoiding it completely ...In statistics , a sampling frame is the source material or device from which a Sampling statistics sample is drawn. ref name S rndalSwensson2003 cite book author1 Carl Erik S rndal author2 Bengt Swensson author3 Jan Wretman title Model assisted survey sampling url http books.google.com books?id ufdONK3E1TcC ... include individuals, households or institutions. ref name S rndalSwensson2003 Importance of the sampling ... of faulty frames, have ended in a disaster or in cloud of doubt. Raymond James Jessen Sampling ... sampling . ref name S rndalSwensson2003 However, in many other cases this is not possible either because ... access to the selected sampling Statistical unit units . ref name S rndalSwensson2003 A frame may also ... sampling, a sampling frame more advanced sample techniques, such as stratified sampling may contain .... An ideal sampling frame will have the following qualities ref name S rndalSwensson2003 all units ... the frame has additional information about the units that allow the use of more advanced sampling frames ... sampling frames include a electoral register or a telephone directory . Other sampling frames ... 9780761943631 pages 28 ref On a more practical levels, sampling frames have the form of computer ... storing data for every unit in the population, only for a smaller number of clusters. Sampling frames problems The sampling frame must be representative of the population and this is a question outside ... of less efficient sampling methods and or making it harder to interpret the resulting data. Statistical ... four basic problems of sampling frames ref name Kish1995 cite book author Leslie Kish title Survey sampling url http books.google.com books?id St nQgAACAAJ accessdate 11 January 2011 year 1995 publisher ... or clusters The frame lists clusters instead of individuals. References reflist Category Sampling statistics ... more details
Unreferenced date July 2007 In audit ing, sampling is an inevitable means of testing. However, sampling is always associated with sampling risks which auditors have to control. Sampling risk represents the possibility that auditor s conclusion based on a sample is different from that reached if the entire population were subject to audit procedure. The auditor may conclude that material misstatements exist, in fact they do not or material misstatements do not exist but in fact they do exist. Auditor can lower the sampling risk by increasing the Sample size sampling size . Non sampling risk includes factors that cause auditors to reach a conclusion other than the sampling size. Interpreting Misinterpretation of evidence and inappropriate Procedure term procedures are good examples. Changing of the sampling size would not reduce non sampling risk. See also Sample statistics DEFAULTSORT Sampling Risk Category Sampling statistics Category Actuarial science Category Risk ... more details
In the theory of finite population sampling , Bernoulli sampling is a sampling process where each element of the statistical population population that is sampled is subjected to an statistical independence independent Bernoulli trial which determines whether the element becomes part of the sample during the drawing of a single sample. An essential property of Bernoulli sampling is that all elements of the population have equal probability of being included in the sample during the drawing of a single sample. Bernoulli sampling is therefore a special case of Poisson sampling , where each element of the population may have a different probability of being included in the sample. Because each element of the population is considered separately for the sample, the sample size is not fixed but rather follows a binomial distribution . See also Poisson sampling Bernoulli trial Bernoulli process Sampling design Further reading Sarndal, Swenson, and Wretman 1992 , Model Assisted Survey Sampling, Springer Verlag, ISBN 0 387 40620 4 Category Sampling statistics Category Sampling techniques ... more details
In the theory of finite population sampling statistics sampling , a sampling design specifies for every possible sample statistics sample its probability of being drawn. Mathematics Mathematically , a sampling design is denoted by the function math P S math which gives the probability of drawing a sample math S. math An example of a sampling design During Bernoulli sampling , math P S math is given by math P S q N text sample S times 1 q N text pop N text sample S math where for each element math q math is the probability of being included in the sample and math N text sample S math is the total number of elements in the sample math S math and math N text pop math is the total number of elements in the population before sampling commenced . See also Statistical sampling Bernoulli sampling Further reading Sarndal, Swenson, and Wretman 1992 , Model Assisted Survey Sampling, Springer Verlag, ISBN 0 387 40620 4 Category Sampling statistics statistics stub ... more details
In the theory of finite population sampling , Poisson sampling is a sampling statistics sampling process where each element of the statistical population population that is sampled is subjected to an statistical independence independent Bernoulli trial which determines whether the element becomes part of the sample during the drawing of a single sample. Each element of the population may have a different probability of being included in the sample. The probability of being included in a sample during the drawing of a single sample is denoted as the first order inclusion probability of that element. If all first order inclusion probabilities are equal, Poisson sampling becomes equivalent to Bernoulli sampling , which can therefore be considered to be a special case of Poisson sampling. A mathematical consequence of Poisson sampling Mathematically, the first order inclusion probability of the i th element of the population is denoted by the symbol sub i sub and the second order inclusion probability that a pair consisting of the i th and j th element of the population that is sampled is included in a sample during the drawing of a single sample is denoted by sub ij sub . The following relation is valid during Poisson sampling math pi ij pi i times pi j . , math See also Bernoulli sampling Poisson distribution Poisson process Sampling design Further reading Sarndal, Swenson, and Wretman 1992 , Model Assisted Survey Sampling, Springer Verlag, ISBN 0 387 40620 4 Category Sampling statistics Category Sampling techniques ... more details
In empirical research , reporting bias refers to a tendency to under report unexpected or undesirable experimental results, attributing the results to sampling statistics sampling or measurement error, while being more trusting of expected or desirable results, though these may be subject to the same sources of error. Over time, reporting bias can lead to a status quo where multiple investigators discover and discard the same results, and later experimenters justify their own reporting bias by observing that previous experimenters reported different results. Thus, each incident of reporting bias can make future incidents more likely. ref http www.cochrane.org resources handbook Green S, Higgins S, editors Glossary. Cochrane Handbook for Systematic Reviews of Interventions 4.2.5. ref ref http www.trialsjournal.com content pdf 1745 6215 11 37.pdf McGauran N, Wieseler B, Kreis J, Sch ler YB, K lsch H, Kaiser T. Reporting bias in medical research a narrative review. Trials. 2010 11 37. doi 10.1186 1745 6215 11 37 ref Type of reporting bias Publication bias The publication or nonpublication of research findings, depending on the nature and direction of the results. Time lag bias The rapid .... Multiple duplicate publication bias The multiple or singular publication of research findings, depending on the nature and direction of the results. Location bias The publication of research findings ... and direction of results. Citation bias The citation or non citation of research findings, depending on the nature and direction of the results. Language bias The publication of research findings ... bias The selective reporting of some outcomes but not others, depending on the nature and direction ... Wiley year 2008 pages 297 334 isbn 9780470699515 ref See also Confirmation bias Funding bias Meta analysis Publication bias Peer review Selection bias References references Biases Category Academic publishing Category Bias Category Research methods Category Systematic review es Sesgo de informaci n ... more details
Other uses Sampling disambiguation Sampling In medicine , sampling is gathering of matter from the body to aid in the process of a medical diagnosis and or evaluation of an indication medicine indication for treatment, further medical test s or other procedures. In this sense, the sample is the gathered matter, and the sampling tool or sampler is the person or material to collect the sample. Sampling is a prerequisite for many medical test s, but generally not for medical history , physical examination and radiologic test s. By types of sampled matter Biopsy A biopsy is the removal of Biological tissue tissue s from the body, generally in the sense of solid or soft tissue targets. Cytopathologic sampling anchor aspiration Cytopathology Cytopathologic sampling particularly involves gathering of cells to detect abnormalities, generally not preserving the normal tissue structure. Puncture also called centesis followed by aspiration is the main method used for cytopathologic sampling. The main method is fine needle aspiration , but there are also somewhat differently designed needles, such as for bone marrow aspiration . Body fluid sampling Body fluid sampling include anchor blood Blood sampling for any blood test , including Artery Arterial blood sampling, such as by radial artery puncture Capillary blood sampling, such as by using a blood lancet Venous blood sampling, also called venipuncture Blood sampling techniques include using a blood lancet , Lumbar puncture to sample cerebrospinal fluid Thoracocentesis to sample pleural fluid Amniocentesis to sample amniotic fluid Microbiological sampling Medical microbiology Microbiological sampling include Blood sampling for blood culture s, performed similarly as that for tests on the fluid itself above anchor swab Throat swab for throat culture . It s performed by applying a cotton swab to the surface of the throat . anchor brush Sampling of sputum from the lungs for sputum culture . It can be performed by special techniques ... more details
In economics and social policy , infrastructure bias refers to the fact that the location and availability of pre existing infrastructure such as roads and telecommunications facilities influences social and economic development. In science , infrastructure bias refers to the influence of existing social or scientific infrastructure on scientific observations. In astronomy and particle physics , where the availability of particular kinds of telescopes or particle accelerators acts as a constraint on the types of experiments that can be done, the data that can be retrieved is biased towards that which can be obtained by the equipment. Procedural bias , related to infrastructure bias, is shown by a case of irregular genetic sampling of Bolivian wild potato es. ref name DivaGIS cite web url http www.diva gis.org docs bias.pdf title Assessing the geographic representativeness of genebank collections The case of Bolivian wild potatoes publisher Diva Geographic Information System ref A 2000 report of previous studies sampling found that 60 of samples had been taken near towns or roads, where 22 would be the average, had the samples been taken at random, ref name DivaGIS or from equidistant points, or at specifically varying distances from towns, representative of the average terrain density . References reflist sci stub Category Bias Category Infrastructure ... more details
Response bias is a type of cognitive bias which can affect the results of a statistical survey if respondents answer questions in the way they think the questioner wants them to answer rather than according to their true belief s. This may occur if the questioner is obviously angling for a particular answer as in push polling or if the respondent wishes to please the questioner by answering what appears to be the morally right answer. An example of the latter might be if a woman surveys a man on his attitudes to domestic violence , or someone who obviously cares about the natural environment environment asks people how much they value a wilderness area . This occurs most often in the wording of the question . Response bias is present when a question contains a leading opinion. For example, saying Given that at the age of 18 people are old enough to fight and die for your country, don t you think they should be able to drink alcohol as well? may yield a response bias, in comparison with simply Do you think 18 year olds should be able to drink alcohol? It also occurs in situations of voluntary response, such as phone in polls, where the people who care enough to call are not necessarily a statistically representative sample of the actual population. Non response bias is not the opposite of response bias and is not a type of cognitive bias it occurs in a statistical survey if those who respond to the survey differ in the outcome variable for example, evaluation of the need for financial ... of the results. See also Total survey error Acquiescence bias Compound question Heckman correction ... Potential for inaccuracy Opinion poll Social desirability bias External links http nces.ed.gov pubsearch pubsinfo.asp?pubid 9613 Estimation of Response Bias in the NHES 95 Adult Education Survey http www.srs.fs.usda.gov pubs 20254 Effects of road sign wording on visitor survey non response bias Category Cognitive biases Category Sampling statistics Statistics stub de Antworttendenz he ... more details
Cluster Sampling is a sampling statistics sampling technique used when natural groupings are evident ... each of these groups. A common motivation for cluster sampling is to reduce the average cost per interview ... exhaustive. A random sampling technique is then used on any relevant clusters to choose which clusters to include in the study. In single stage cluster sampling, all the elements from each of the selected clusters are used. In two stage cluster sampling, a random sampling technique is applied to the elements from each of the selected clusters. The main difference between cluster sampling and stratified sampling is that in cluster sampling the cluster is treated as the sampling unit so analysis is done on a population of clusters at least in the first stage . In stratified sampling, the analysis is done on elements within strata. In stratified sampling, a random sample is drawn from each of the strata, whereas in cluster sampling only the selected clusters are studied. The main objective of cluster sampling is to reduce costs by increasing sampling efficiency. This contrasts with stratified sampling where the main objective is to increase precision. There also exists multistage sampling , where more than two steps are taken in selecting clusters from clusters. Aspects of cluster sampling One version of cluster sampling is area sampling or geographical cluster sampling . Clusters ... to survey, greater economy than simple random sampling can be achieved by treating several respondents ... sampling is used. In this method, the probability of selecting any cluster varies with the size of the cluster ... probability of selection. Cluster sampling is used to estimate high mortalities in cases such as war ... than other methods e.g. fewer travel expenses, administration costs Disadvantages Higher sampling ... , 316, 1455 1460. ref See also Sampling statistics Multistage sampling Simple random sampling References Reflist DEFAULTSORT Cluster Sampling Category Sampling techniques Category Market research de ... more details
In sampling theory , sampling fraction is the ratio of sample size to population size or, in the context of stratified sampling , the ratio of the sample size to the size of the stratum. ref cite book last Dodge first Yadolah title The Oxford Dictionary of Statistical Terms publisher Oxford University Press location Oxford date 2003 isbn 0 19 920613 9 language English ref The formula for the sampling fraction is math f frac n N , math where n is the sample size and N is the population size. If the sampling fraction is less than 5 , then the finite population effect might be ignored. clarify date January 2012 References references Category Sampling statistics Category Statistical ratios Statistics stub ... more details
Quota sampling is a method for selecting survey participants. In quota sampling, a population is first segmented into mutually exclusive sub groups, just as in stratified sampling . Then judgment is used to select the subjects or units from each segment based on a specified proportion. For example, an interviewer may be told to sample 200 females and 300 males between the age of 45 and 60. This means that individuals can put a demand on who they want to sample targeting This second step makes the technique non probability sampling. In quota sampling, the selection of the sample is non random sample and can be Reliability statistics unreliable . For example, interviewers might be tempted to interview those people in the street who look most helpful, or may choose to use accidental sampling to question those closest to them, for time keeping sake. The problem is that these samples may be biased because not everyone gets a chance of selection. This non random element is a source of uncertainty about the nature of the actual sample and quota versus probability has been a matter of controversy for many years. ref http www.fao.org docrep W3241E w3241e08.htm quota 20sampling Marketing Research and Information Systems. Marketing and Agribusiness Texts 4 ref Quota sampling is useful when time is limited, a sampling frame is not available, the research budget is very tight or when detailed accuracy is not important. Subsets are chosen and then either convenience or judgment sampling is used to choose people from each subset. The researcher decides how many of each category is selected. Quota sampling is the non probability version of stratified sampling. In stratified sampling, subsets of the population are created so that each subset has a common characteristic, such as gender. Random sampling chooses a number of subjects from each subset with, unlike a quota sample, each potential ... Sampling techniques de Quotenstichprobe ru ... more details
Theoretical sampling refers to the process of choosing new research sites or cases to compare with ones that have already been studied. It is one of the tools of qualitative research . The term was coined by Barney Glaser and Anselm Strauss in 1967. The goal of theoretical sampling is not the same as with the sampling statistics probabilistic sampling the researcher s goal is not the representative capture of all possible variations, but to gain a deeper understanding of analysed cases and facilitate the development of analytic frame and concept s used in their research. Theoretical sampling can be viewed as a technique of data triangulation using independent pieces of information to get a better fix on something that is only partially known or understood. See also Grounded theory Sampling statistics Sampling case studies References Charles C. Ragin , Constructing Social Research The Unity and Diversity of Method , Pine Forge Press, 1994, ISBN 0 8039 9021 9 Barney G. Glaser & Anselm L. Strauss , The Discovery of Grounded Theory Strategies for Qualitative Research , Chicago, Aldine Publishing Company, 1967, ISBN 0 202 30260 1 Category Sociological terms ... more details
Encyclopedia
top
