confounding
31Medical analysis of circumcision — Numerous medical studies have examined the effects of male circumcision with mixed opinions regarding the benefits and risks of the procedure. Opponents of circumcision say it is medically unnecessary, is unethical when performed on newborns, is… …
32Dual energy X-ray absorptiometry — (DXA, previously DEXA) is a means of measuring bone mineral density (BMD). Two X ray beams with differing energy levels are aimed at the patient s bones. When soft tissue absorption is subtracted out, the BMD can be determined from the absorption …
33Cohort study — For other senses of this word, see cohort (disambiguation). A cohort study or panel study is a form of longitudinal study (a type of observational study) used in medicine, social science, actuarial science, and ecology. It is an analysis of risk… …
34Student's t-test — A t test is any statistical hypothesis test in which the test statistic follows a Student s t distribution if the null hypothesis is supported. It is most commonly applied when the test statistic would follow a normal distribution if the value of …
35Covariate — In statistics, a covariate is a variable that is possibly predictive of the outcome under study. A covariate may be of direct interest or it may be a confounding or interacting variable. The alternative terms explanatory variable, independent… …
36Internal validity — is the validity of (causal) inferences in scientific studies, usually based on experiments as experimental validity [ Mitchell, M. and Jolley, J. (2001). Research Design Explained (4th Ed) New York:Harcourt.] . Details Inferences are said to… …
37Scientific control — Take identical growing plants and give fertilizer to half of them. If there are differences between the fertilized plant group and the unfertilized control group, these differences may be due to the fertilizer. Scientific control allows for… …
38Alcohol and cancer — Total recorded alcohol per capita consumption (15+), in litres of pure alcohol.[1] Alcohol is associated with an increased risk of a number of cancers.[2] 3.6% of all cancer cases and 3.5% of cancer deaths worldwide are attributable to consu …
39Crossover 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… …
40Efficacy of prayer — Measuring the efficacy of prayer has been attempted in various studies since Francis Galton first addressed the subject (partly as satire) in 1872.Francis Galton, [http://www.abelard.org/galton/galton.htm Statistical Inquiries into the Efficacy… …
