Biomaterial Database

A note on the interpretation of results of supplementation trials. 1980

J Lee

In a supplementation trial to study the effect of the supplemental treatment on some response variable of interest, the variable is often measured twice from each subject, namely; before (x) and after (y) the trial period. The difference between y and x (Z = y - x) is then computed for each subject. The Z and x values are the primary data for statistical analysis. The objective of the study is to obtain an unbiased estimate of the "average effect" of the supplemental treatment on the response variable. When x is not comparable in the two groups (supplementation versus no supplementation) but x and Z are similarly correlated in the two groups, then an unbiased estimate of the average effect is obtained by the usual method of covariance adjustment of x. However, when x and Z are not similarly correlated in the two groups, a modified method of adjustment of x is needed to obtain an unbiased estimate of the average effect. The modified method is given in this note. Furthermore, the statistical implication of the average effect so obtained is discussed.

UI	MeSH Term	Description	Entries
D008954	Models, Biological	Theoretical representations that simulate the behavior or activity of biological processes or diseases. For disease models in living animals, DISEASE MODELS, ANIMAL is available. Biological models include the use of mathematical equations, computers, and other electronic equipment.	Biological Model,Biological Models,Model, Biological,Models, Biologic,Biologic Model,Biologic Models,Model, Biologic
D012044	Regression Analysis	Procedures for finding the mathematical function which best describes the relationship between a dependent variable and one or more independent variables. In linear regression (see LINEAR MODELS) the relationship is constrained to be a straight line and LEAST-SQUARES ANALYSIS is used to determine the best fit. In logistic regression (see LOGISTIC MODELS) the dependent variable is qualitative rather than continuously variable and LIKELIHOOD FUNCTIONS are used to find the best relationship. In multiple regression, the dependent variable is considered to depend on more than a single independent variable.	Regression Diagnostics,Statistical Regression,Analysis, Regression,Analyses, Regression,Diagnostics, Regression,Regression Analyses,Regression, Statistical,Regressions, Statistical,Statistical Regressions
D002986	Clinical Trials as Topic	Works about pre-planned studies of the safety, efficacy, or optimum dosage schedule (if appropriate) of one or more diagnostic, therapeutic, or prophylactic drugs, devices, or techniques selected according to predetermined criteria of eligibility and observed for predefined evidence of favorable and unfavorable effects. This concept includes clinical trials conducted both in the U.S. and in other countries.	Clinical Trial as Topic
D004032	Diet	Regular course of eating and drinking adopted by a person or animal.	Diets
D005527	Food, Fortified	Any food that has been supplemented with essential NUTRIENTS either in quantities that are greater than those normally present, or which are not found in the food typically. Fortified food also includes food enriched by adding various nutrients to compensate for those removed by refinement or processing. (Modified from Segen, Dictionary of Modern Medicine, 1992).	Enriched Food,Food, Supplemented,Enriched Foods,Food, Enriched,Foods, Enriched,Foods, Fortified,Foods, Supplemented,Fortified Food,Fortified Foods,Supplemented Food,Supplemented Foods
D013223	Statistics as Topic	Works about the science and art of collecting, summarizing, and analyzing data that are subject to random variation.	Area Analysis,Estimation Technics,Estimation Techniques,Indirect Estimation Technics,Indirect Estimation Techniques,Multiple Classification Analysis,Service Statistics,Statistical Study,Statistics, Service,Tables and Charts as Topic,Analyses, Area,Analyses, Multiple Classification,Area Analyses,Classification Analyses, Multiple,Classification Analysis, Multiple,Estimation Technic, Indirect,Estimation Technics, Indirect,Estimation Technique,Estimation Technique, Indirect,Estimation Techniques, Indirect,Indirect Estimation Technic,Indirect Estimation Technique,Multiple Classification Analyses,Statistical Studies,Studies, Statistical,Study, Statistical,Technic, Indirect Estimation,Technics, Estimation,Technics, Indirect Estimation,Technique, Estimation,Technique, Indirect Estimation,Techniques, Estimation,Techniques, Indirect Estimation