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Conditional Logistic Regression
Conditional logistic regression is an extension of logistic regression that allows one to take into account stratification and matching. Its main field of application is observational studies and in particular epidemiology. It was devised in 1978 by Norman Breslow, Nicholas Day, Katherine Halvorsen, Ross L. Prentice and C. Sabai. It is the most flexible and general procedure for matched data. Motivation Observational studies use stratification or matching as a way to control for confounding. Several tests existed before conditional logistic regression for matched data as shown in related tests. However, they did not allow for the analysis of continuous predictors with arbitrary stratum size. All of those procedures also lack the flexibility of conditional logistic regression and in particular the possibility to control for covariates. Logistic regression can take into account stratification by having a different constant term for each stratum. Let us denote Y_\in\ the lab ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Logistic Regression
In statistics, the logistic model (or logit model) is a statistical model that models the probability of an event taking place by having the log-odds for the event be a linear combination of one or more independent variables. In regression analysis, logistic regression (or logit regression) is estimating the parameters of a logistic model (the coefficients in the linear combination). Formally, in binary logistic regression there is a single binary dependent variable, coded by an indicator variable, where the two values are labeled "0" and "1", while the independent variables can each be a binary variable (two classes, coded by an indicator variable) or a continuous variable (any real value). The corresponding probability of the value labeled "1" can vary between 0 (certainly the value "0") and 1 (certainly the value "1"), hence the labeling; the function that converts log-odds to probability is the logistic function, hence the name. The unit of measurement for the log-o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stratification (clinical Trials)
Stratification of clinical trials is the partitioning of subjects and results by a factor other than the treatment given. Stratification can be used to ensure equal allocation of subgroups of participants to each experimental condition. This may be done by gender, age, or other demographic factors. Stratification can be used to control for confounding variables (variables other than those the researcher is studying), thereby making it easier for the research to detect and interpret relationships between variables. For example, if doing a study of fitness where age or gender was expected to influence the outcomes, participants could be stratified into groups by the confounding variable. A limitation of this method is that it requires knowledge of what variables need to be controlled. Types of stratification Stratified random sampling designs divide the population into homogeneous strata, and an appropriate number of participants are chosen at random from each stratum. Prop ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Matching (statistics)
Matching is a statistical technique which is used to evaluate the effect of a treatment by comparing the treated and the non-treated units in an observational study or quasi-experiment (i.e. when the treatment is not randomly assigned). The goal of matching is to reduce bias for the estimated treatment effect in an observational-data study, by finding, for every treated unit, one (or more) non-treated unit(s) with similar observable characteristics against which the covariates are balanced out. By matching treated units to similar non-treated units, matching enables a comparison of outcomes among treated and non-treated units to estimate the effect of the treatment reducing bias due to confounding. Propensity score matching, an early matching technique, was developed as part of the Rubin causal model, but has been shown to increase model dependence, bias, inefficiency, and power and is no longer recommended compared to other matching methods. Matching has been promoted by Donald Rub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Observational Studies
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 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. Motivation The independent variable may be beyond the control of the investigator for a variety of reasons: * A randomized experiment would violate ethical standards. Suppose one wanted to investigate the abortion – breast cancer h ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Epidemiology
Epidemiology is the study and analysis of the distribution (who, when, and where), patterns and determinants of health and disease conditions in a defined population. It is a cornerstone of public health, and shapes policy decisions and evidence-based practice by identifying risk factors for disease and targets for preventive healthcare. Epidemiologists help with study design, collection, and statistical analysis of data, amend interpretation and dissemination of results (including peer review and occasional systematic review). Epidemiology has helped develop methodology used in clinical research, public health studies, and, to a lesser extent, basic research in the biological sciences. Major areas of epidemiological study include disease causation, transmission, outbreak investigation, disease surveillance, environmental epidemiology, forensic epidemiology, occupational epidemiology, screening, biomonitoring, and comparisons of treatment effects such as in c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Norman Breslow
Norman Edward Breslow (February 21, 1941 – December 9, 2015) was an American statistician and medical researcher. At the time of his death, he was Professor (Emeritus) of Biostatistics in the School of Public Health, of the University of Washington. He is co-author or author of hundreds of published works during 1967 to 2015. Among his many accomplishments is his work with co-author Nicholas Day that developed and popularized the use of case-control matched sample research designs, in the two-volume work ''Statistical Methods in Cancer Research''. This was with view that matched sample studies have a role within larger program of many types of studies, in making progress on a vast and important problem like cancer. Matched sample studies can quickly and cheaply test some hypothesized relationships, but their apparent findings are not definitive, and there's much they cannot accomplish. Their results, however, can inform the design of slow and expensive longitudinal larg ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nick Day (statistician)
Nicholas Edward Day, CBE, FRS (born 24 September 1939) is a retired statistician and cancer epidemiologist. Education He was educated at Gresham's School and the University of Oxford, from 1958-1962, where he gained a B.A. in Mathematics and a Diploma in Statistics, and the University of Aberdeen from 1962-1966, where he obtained a Doctorate of Philosophy. Career Day worked at the International Agency for Research on Cancer in Lyon from 1969 to 1986, where he rose to become head of the Unit of Biostatistics and Field Studies. He was director of the Medical Research Council Biostatistics Unit from 1986 to 1989, and continued as honorary director until 1999. From 1997 until his retirement in 2004 he was co-director of the Strangeways Research Laboratory in Cambridge. He was also professor of public health at the University of Cambridge from 1989 to 1999, and professor of epidemiology from 1999 until 2004. Day was made a Commander of the Order of the British Empire in the 2001 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Katherine Halvorsen
Katherine Taylor Halvorsen is an American statistician and statistics educator whose research topics have included statistical significance for contingency tables, and the conditional logistic regression method for analysis of multiple risk factors in case–control studies. She was co-author of four editions of ''Mathematics Education in the United States'', a quadrennial review publication of the National Council of Teachers of Mathematics, and serves on the Mathematical Sciences Academic Advisory Committee of the College Board. Education and career Halvorsen is a graduate of the University of Michigan. After earning master's degrees from Boston University and in 1978, the University of Washington, she completed her Ph.D. in biostatistics in 1984 at the Harvard School of Public Health, with the dissertation ''Estimating Population Parameters Using Information from Several Independent Sources'' supervised by Frederick Mosteller. She is a professor emerita of mathematics and s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ross L
Ross or ROSS may refer to: People * Clan Ross, a Highland Scottish clan * Ross (name), including a list of people with the surname or given name Ross, as well as the meaning * Earl of Ross, a peerage of Scotland Places * RoSS, the Republic of South Sudan Antarctica * Ross Sea * Ross Ice Shelf * Ross Dependency Australia * Ross, Tasmania Chile * Ross Casino, a former casino in Pichilemu, Chile; now the Agustín Ross Cultural Centre Ireland *"Ross", a common nickname for County Roscommon * Ross, County Mayo, a townland in Killursa civil parish, barony of Clare, County Mayo, bordering Moyne Townland * Ross, County Westmeath, a townland in Noughaval civil parish, barony of Kilkenny West, County Westmeath * Ross, County Wexford * The Diocese of Ross in West Cork. The Roman Catholic diocese merged with Cork in 1958 to become the Roman Catholic Diocese of Cork and Ross, while the Church of Ireland diocese is now part of the Diocese of Cork, Cloyne and Ross. This area, centered ar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Confounding
In statistics, a confounder (also confounding variable, confounding factor, extraneous determinant or lurking variable) is a variable that influences both the dependent variable and independent variable, causing a spurious association. Confounding is a causal concept, and as such, cannot be described in terms of correlations or associations.Pearl, J., (2009). Simpson's Paradox, Confounding, and Collapsibility In ''Causality: Models, Reasoning and Inference'' (2nd ed.). New York : Cambridge University Press. The existence of confounders is an important quantitative explanation why correlation does not imply causation. Confounds are threats to internal validity. Definition Confounding is defined in terms of the data generating model. Let ''X'' be some independent variable, and ''Y'' some dependent variable. To estimate the effect of ''X'' on ''Y'', the statistician must suppress the effects of extraneous variables that influence both ''X'' and ''Y''. We say that ''X' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Related Tests
''Related'' is an American comedy-drama television series that aired on The WB from October 5, 2005, to March 20, 2006. It revolves around the lives of four close-knit sisters of Italian descent, raised in Brooklyn and living in Manhattan. The show was created by former ''Sex and the City'' writer Liz Tuccillo, and executive produced by ''Friends'' co-creator Marta Kauffman. Despite heavy promotion, initial ratings did not warrant the show being picked up for a second season when The WB network was folded into The CW. Cast and characters Main * Jennifer Esposito as Ginnie, the oldest of the Sorelli sisters. She is an ambitious 30-year-old corporate attorney and the only sister who is married. In the premiere episode, Ginnie learned that she was pregnant, but she subsequently lost the baby. * Kiele Sanchez as Ann, the second-oldest sister. She is a 26-year-old therapist who specializes in counseling transvestites. * Lizzy Caplan as Marjee, who is 23 years old. At the beginning ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Maximum Likelihood Estimation
In statistics, maximum likelihood estimation (MLE) is a method of estimating the parameters of an assumed probability distribution, given some observed data. This is achieved by maximizing a likelihood function so that, under the assumed statistical model, the observed data is most probable. The point in the parameter space that maximizes the likelihood function is called the maximum likelihood estimate. The logic of maximum likelihood is both intuitive and flexible, and as such the method has become a dominant means of statistical inference. If the likelihood function is differentiable, the derivative test for finding maxima can be applied. In some cases, the first-order conditions of the likelihood function can be solved analytically; for instance, the ordinary least squares estimator for a linear regression model maximizes the likelihood when all observed outcomes are assumed to have Normal distributions with the same variance. From the perspective of Bayesian inference ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
