Principal Components and Factor Analysis

Click the Review correlations, means, standard deviations button on the Define Method of Factor Extraction dialog box - Descriptives tab to display the Review Descriptive Statistics dialog box. The number of tabs available depends on the Input File format selected on the Factor Analysis Startup Panel - Quick tab. If Raw Data is selected as the Input File, four tabs are available: Quick, Advanced, Pairwise, and Save. If Correlation Matrix is selected as the Input File, three tabs are available: Quick, Advanced, and Save. Use the options in the Review Descriptive Statistics dialog box to compute detailed descriptive statistics for the variables in the current analysis. Note that two important underlying assumptions of factor analysis are 1) that the distributions of variables follow the normal distribution, and 2) that the correlations between variables are linear. The graphics options on this dialog allow you to visually test both of those assumptions. (The graphics options are not available if a correlation matrix input file is currently analyzed).

Summary box. The Summary box at the top of the dialog box displays a general summary of the current analysis.

Copy button. Click the Copy button to copy either the selected text (if text has been selected) in the Summary box or all of the text (if no text has been selected) to the Clipboard. Note that the copied text retains formatting information (such as font, color, etc.).

Contract/Expand button. Click the Contract/Expand button to contract or expand the Summary box. When contracted, you can see only one line of the Summary box text and can scroll through the text using a scroll bar. Note that when contracted the text is scrolled so that the first non-blank line is at the top. When expanded (the default setting), the entire Summary box will be displayed in the Review Descriptive Statistics dialog box.

Correlations. Click the Correlations button to produce a spreadsheet with the current correlation matrix. If a raw data file is analyzed, a Graph of Input Data for that spreadsheet is the scatterplot with the fitted regression line. If matrix ill-conditioning was detected during the factoring process, this matrix will have been slightly modified (see Note).

Cancel. Click the Cancel button to return to the Define Method of Factor Extraction dialog box.

Options. Click the Options button to display the Options menu.

Note: matrix ill-conditioning and the modified correlation matrix. The Introductory Overviews discuss the issue of matrix ill-conditioning. If during the factoring process the message is displayed that the correlation matrix could not be inverted, then subsequently, when you click the Correlations button in the Review Descriptive Statistics dialog box, the correlation matrix will have been modified (to allow inversion). Specifically, a small constant was added to the diagonal of the correlation matrix until the determinant of that matrix was greater than 1.e-50. The modified (slightly lowered) correlations will be reported here if matrix ill conditioning was detected and the modification performed.