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Stepwise Procedures In Discriminant Analysis
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CHAPTER FOUR DATA ANALYSIS
METHOD OF DATA COLLECTION
The data employed in this work are as collected by G.R. Bryce and
R.M. Barker of Brigham Young University as part of a preliminary study of a possible link between football helmet design and neck injuries.
Five head measurements were made on each subject, about 30 subjects per group:
Group 1 = High School Football players Group 2 = Non-football players
The five variables are
WDIM = X1 = head width at widest dimension
CIRCUM = X2 = head circumference
FBEYE = X3 = front to back measurement at eye level
EYEHD = X4 = eye-to-top-of-head measurement
EARHD = X5 = ear-to-top-of-head measurement
Discriminant analysis and stepwise discriminant analysis were both carried on the data sets using SPSS. There are about 30 samples in each group. The data for the analysis are shown in appendix 1.
DISCRIMINANT
/GROUPS=Group(1 2)
/VARIABLES=WDIM CIRCUM FBEYE EYEHD EARHD
/ANALYSIS ALL
/SAVE=CLASS SCORES PROBS
/PRIORS EQUAL
/STATISTICS=MEAN STDDEV UNIVF COEFF RAW CORR COV GCOV TCOV TABLE CROSSVALID
/CLASSIFY=NONMISSING POOLED .
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ABSRACT - [ Total Page(s): 1 ]
Abstract
Several multivariate measurements require variables
selection and ordering. Stepwise procedures ensure a step by step method
through which these variables are selected and ordered usually for
discrimination and classification purposes. Stepwise procedures in discriminant
analysis show that only important variables are selected, while redundant
variables (variables that contribute less in the presence of other variables) are
discarded. The use of stepwise procedures ... Continue reading---
APPENDIX A - [ Total Page(s): 1 ] ... Continue reading---
APPENDIX B - [ Total Page(s): 1 ] APPENDIX II BACKWARD ELIMINATION METHOD The procedure for the backward elimination of variables starts with all the x’s included in the model and deletes one at a time using a partial  or F. At the first step, the partial  for each xi isThe variable with the smallest F or the largest  is deleted. At the second step of backward elimination of variables, a partial  or F is calculated for each q-1 remaining variables and again, the variable which is th ... Continue reading---
TABLE OF CONTENTS - [ Total Page(s): 1 ]TABLE OF CONTENTSPageTitle PageApproval pageDedicationAcknowledgementAbstractTable of ContentsCHAPTER 1: INTRODUCTION1.1 Discriminant Analysis1.2 Stepwise Discriminant analysis1.3 Steps Involved in discriminant Analysis1.4 Goals for Discriminant Analysis1.5 Examples of Discriminant analysis problems1.6 Aims and Obj ectives1.7 Definition of Terms1.7.1 Discriminant function1.7.2 The eigenvalue1.7.3 Discriminant Score1.7.4 Cut off1.7 ... Continue reading---
CHAPTER ONE - [ Total Page(s): 2 ] DEFINITION OF TERMS Discriminant Function This is a latent variable which is created as a linear combination of discriminating variables, such that Y = L1X1 + L2X2 + + Lp Xp where the L’s are the discriminant coefficients, the x’s are the discriminating variables. The eigenvalue: This is the ratio of importance of the dimensions which classifies cases of the dependent variables. There is one eigenvalue for each discriminant functio ... Continue reading---
CHAPTER TWO - [ Total Page(s): 3 ] 5 is called the mahalanobis (squared) distance for known parameters. For unknown parameters, the Mahalanobis (squared) distance is obtained by estimating p1, p2 and S by X1, X2 and S, respectively. Following the same technique the Mahalanobis (Squared) distance, D , for the unknown parameters is D2 = (X- X)+S-1 (X1- X2) . The distribution of D can be used to test if there are significant differences between the two groups.2.4 WELCH’S CRITERION Welch (1939) suggest ... Continue reading---
CHAPTER THREE - [ Total Page(s): 5 ]The addition of variables reduces the power of Wilks’ Λ test statistics except if the added variables contribute to the rejection of Ho by causing a significant decrease in Wilks’ Λ ... Continue reading---
CHAPTER FIVE - [ Total Page(s): 1 ]CHAPTER FIVERESULTS, CONCLUSION AND RECOMMENDATIONRESULTSAs can be observed from the results of the analysis, when discriminant analysis was employed, the variable CIRCUM(X2) has the highest Wilks’ lambda of 0.999 followed by FBEYE (X2) (0.959). The variable EYEHD (X4) has the least Wilks’ lambda of 0.517 followed by EARHD (X5) (0.705). Also the least F-value was recorded with the variable CIRCUM (X2) (0.074) followed by the variable FBEYE (X2) (2.474), while the variable EYEHD (X4 ... Continue reading---
REFRENCES - [ Total Page(s): 1 ] REFERENCES Anderson, T.W. (1958). An introduction to multivariate statistical Analysis. John Wiley & Sons Inc., New York. Cohen, J. (1968). Multiple regression as a general data-analytic system. Psychological Bulletin 70, 426-443. Cooley W.W. and Lohnes P.R. (1962). Multivariate procedures for the Behavioural Sciences, New York John Wiley and Sons Inc. Efroymson, M.A. (1960). Multiple regression analysis. In A. Raston & H.S. Wilfs (Eds.) Mathematical methods for ... Continue reading---
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ABSRACT - [ Total Page(s): 1 ]
Abstract
Several multivariate measurements require variables
selection and ordering. Stepwise procedures ensure a step by step method
through which these variables are selected and ordered usually for
discrimination and classification purposes. Stepwise procedures in discriminant
analysis show that only important variables are selected, while redundant
variables (variables that contribute less in the presence of other variables) are
discarded. The use of stepwise procedures ... Continue reading---