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Chapter-17 The general linear model and other Multivariate methods

BOOK TITLE: Research Methodology Simplified: Every Clinician a Researcher

Author
1. Parikh Mahendra N
2. Mukherjee Joydev
3. Hazra Avijit
4. Gogtay Nithya
ISBN
9789350250037
DOI
10.5005/jp/books/11435_17
Edition
1/e
Publishing Year
2010
Pages
9
Author Affiliations
1. Seth GS Medical College and Nowrosjee Wadia Maternity Hospital, Mumbai, Seth Gordhandas Sunderdas Medical College, Nowrosjee Wadia Maternity Hospital, Mumbai, Maharashtra, India; Shushrusha Citizens’ Cooperative Hospital, Mumbai, Maharashtra, India; Fertility Sterility, India; The Journal of Obstetrics and Gynaecology of India, Nowrosjee Wadia Maternity Hospital, Mumbai, Mumbai, Maharashtra, India, Mumbai, Seth GS Medical College and Nowrosjee Wadia Maternity Hospital, Mumbai, Maharashtra, India
2. North Bengal Medical College, West Bengal, India, RG Kar Medical College, Kolkota, RG Kar Medical College, Kolkata, India, RG Kar Medical College, Kolkata, RG Kar Medical College, Kolkata, West Bengal, India
3. Institute of Postgraduate Medical Education, and Research, Kolkata, Institute of Postgraduate Medical Education and Research, Kolkata, India, Institute of Postgraduate Medical Education and Research (IPGMER), Kolkata, West Bengal, India
4. Seth Gordhandas Sunderdas Medical College and King Edward Memorial Hospital, Mumbai, Maharashtra, India; Journal of Postgraduate Medicine, Seth GS Medical College and KEM Hospital, Mumbai, India, Department of Clinical Pharmacology, Seth GS Medical College and KEM Hospital, Mumbai, India
Chapter keywords

Abstract

Multivariate analysis refers to statistical techniques that look at a number of variables simultaneously, with a view to clarifying the relationships between them. Many of them try to build mathematical models that can be used for prediction. The general linear model is not a discrete statistical technique in itself, but rather a strategy for analysis. Its goal is to determine whether and how one or more independent variables relate to or affect one or more dependent variables, assuming that the relationships between them are linear. It is an umbrella concept, that in addition to simple linear regression and one-way analysis of variance (ANOVA), includes several multivariate techniques. Multiple linear regression models a situation where a single numerical dependent variable is to be predicted from multiple independent variables. Logistic regression is an analogous technique that is used when the outcome variable is dichotomous in nature. In this, the natural logarithm of odds ratios is modeled as a linear function of the explanatory variables. The log-linear technique models count type of data and can be used to analyze cross-tabulations where more than two variables are included. It can look at three or more variables at the same time to determine associations between them and also show just where these associations lie. Factor analysis and principal component analysis are a group of related techniques that seek to reduce a large number of predictor variables to a smaller number of factors or components, that are linearly related to the original variables. Analysis of covariance (ANCOVA) is an extension of ANOVA, in which an additional independent variable of interest for which data is available, the covariate, is brought into the analysis. It tries to examine whether a difference still persists after ‘controlling’ for the effect of the covariate that can impact the numerical dependent variable of interest. MANOVA and MANCOVA, are multivariate extensions of ANOVA and ANCOVA respectively, and are used when multiple numerical dependent variables have to be incorporated in the analysis.

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