Stratified sampling — In statistics, stratified sampling is a method of sampling from a population.When sub populations vary considerably, it is advantageous to sample each subpopulation (stratum) independently. Stratification is the process of grouping members of the … Wikipedia
National Longitudinal Study of Adolescent Health — The National Longitudinal Study of Adolescent Health (also called Add Health) is the only nationally representative study of adolescent sexuality, which has spawned over one thousand peer reviewed publications on many issues related to adolescent … Wikipedia
Topologically stratified space — In topology, a branch of mathematics, a topologically stratified space is a space X that has been decomposed into pieces called strata; these strata are topological manifolds and are required to fit together in a certain way. Topologically… … Wikipedia
Nested case-control study — A nested case control study is a variation of a case cohort study in which only a subset of controls from the cohort are compared to the incident cases. In a case cohort study, all incident cases in the cohort are compared to a random subset of… … Wikipedia
Clinical study design — is the formulation of trials and experiments in medical and epidemiological research, sometimes known as clinical trials. Many of the considerations here are shared under the more general topic of design of experiments but there can be others, in … Wikipedia
Whitehall Study — The original Whitehall Study investigated social determinants of health, specifically the cardiorespiratory disease prevalence and mortality rates among British male civil servants between the ages of 20 and 64. The initial study, the Whitehall I … Wikipedia
British Doctors Study — The British doctors study is the generally accepted name of a prospective cohort study which has been running from 1951 to 2001, and in 1956 provided convincing statistical proof that tobacco smoking increased the risk of lung… … Wikipedia
Crossover study — A crossover study (also referred to as a crossover trial) is a longitudinal study in which subjects receive a sequence of different treatments (or exposures). While crossover studies can be observational studies, many important crossover studies… … Wikipedia
Observational study — In epidemiology and statistics, an observational study draws inferences 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… … Wikipedia
Sample size determination — is the act of choosing the number of observations to include in a statistical sample. The sample size is an important feature of any empirical study in which the goal is to make inferences about a population from a sample. In practice, the sample … Wikipedia
Earth Sciences — ▪ 2009 Introduction Geology and Geochemistry The theme of the 33rd International Geological Congress, which was held in Norway in August 2008, was “Earth System Science: Foundation for Sustainable Development.” It was attended by nearly… … Universalium
