April 4th, 2024

Conducting and Interpreting Factor Analysis

By Josephine Santos · 11 min read

Psychologist conducting a factor analysis

Overview

Factor Analysis, a powerful statistical method, is akin to cluster analysis but with a twist. While cluster analysis groups similar cases, factor analysis groups similar variables into dimensions, unveiling latent variables or constructs. This technique is pivotal in simplifying complex datasets, especially when the goal is to reduce a plethora of individual items into fewer dimensions.

The Essence of Factor Analysis

Factor Analysis serves multiple purposes:

1. Data Simplification: It's a tool to reduce the number of variables, especially beneficial in regression models.


2. Rotation Methods: Post extraction, factors are usually rotated. Various rotation methods exist, with some ensuring factors remain orthogonal, thus eliminating multicollinearity issues in regression.


3.Scale Verification: Factor analysis aids in verifying scale construction. Confirmatory factor analysis, a subset, is used in structural equation modeling.


4. Index Construction: While the common approach to construct an index is summing up all items, factor analysis can justify dropping certain questions to make questionnaires concise.

Using SPSS for Factor Analysis

To understand the underlying dimensions of standardized and aptitude test scores, SPSS (Statistical Package for the Social Sciences) is a go-to statistical software. Here's a step-by-step guide:

1.) Locate Factor Analysis: Navigate to Analyze > Dimension Reduction > Factor.

SPSS Locate Factor Analysis Analyze - Dimension Reduction - Factor

2.) Add Variables: Insert the standardized tests (math, reading, writing) and aptitude tests (1-5) to the list.

SPSS Factor analysis - Add Variables Box

3.) Descriptives: To verify assumptions, include the KMO test of sphericity and the Anti-Image Correlation matrix.

SPSS Factor Analysis - Descriptives - KMO and Bartlett's test of sphericity

4.) Extraction Method: While SPSS defaults to 'principal components', for identifying latent constructs, 'principal axis factoring' is more apt.

SPSS extraction method - principal axis factoring
5.) Rotation Method: 'Varimax', an orthogonal rotation method, is commonly used. For non-orthogonal factors, 'direct oblimin rotation' is suitable.
SPSS Factor Analysis - Rotation Method - Varimax / Direct Oblimin
6.) Options: Manage missing values, perhaps by replacing them with the mean. Suppress small factor loadings for clarity.
SPSS Factor Analysis - Suppress small coefficients
7.) Save Results: This step generates standardized scores for each extracted factor.

Conclusion

Factor Analysis is an indispensable tool for researchers and analysts aiming to uncover hidden patterns and dimensions in their data. While SPSS offers robust capabilities for factor analysis, it's essential to understand the nuances and steps involved to derive meaningful insights.


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