Introduction Basic Concepts of Principal Components Geometrical Properties of Principal Components Decomposition Properties of Principal Components Principal Components of Patterned Correlation Matrices Rotation of Principal Components Using Principal Components to Select a Subset of Variables Principal Components Versus Factor Analysis Uses of Principal Components in Regression Analysis Using Principal Components to Detect Outlying and Influential Observations Use of Principal Components in Cluster Analysis Use of Principal Components Analysis in Conjunction with Other Multivariate Analysis Procedures Other Techniques Related to Principal Components Summary and Conclusions