Factor Rotation Methods: Orthogonal vs. Oblique Rotations

Introduction to Factor Rotation

Factor rotation plays a key role in factor analysis, a method used to uncover latent variables. After extracting factors, raw loadings are often complex, so rotation redistributes variance to create a clearer factor structure. This aids in understanding relationships between variables and factors.

Factor rotations are divided into two categories: orthogonal and oblique. The main difference between these approaches lies in whether factors are allowed to correlate. Each method has unique benefits and should be chosen based on the characteristics of the data and theoretical considerations.

Orthogonal Rotation

Orthogonal rotations assume that factors are completely independent, with zero correlations between them. This method maintains the factors' independence by constraining them to 90-degree angles. It is particularly useful when factors are expected to be distinct.

The primary advantage of orthogonal rotation is simplicity, as uncorrelated factors make it easier to interpret variable-factor relationships. This approach is often used in fields like economics or engineering where latent variables are theoretically independent.

Types of Orthogonal Rotations

Several methods exist under orthogonal rotations, each offering a different way to redistribute variance:

Varimax: The most popular orthogonal method, varimax maximizes the variance of squared loadings, making each variable load strongly on one factor. This provides clear and distinct factor structures.

Quartimax: This method simplifies the structure by maximizing variance across variables for each factor, often leading to one dominant factor. It is useful when a general factor is expected to explain most of the variance.

Equamax: A hybrid of varimax and quartimax, equamax balances both methods, making it less common but suitable when capturing both distinct and general factors is important.

Oblique Rotation

Oblique rotations, in contrast, allow factors to correlate, which is often more realistic, especially in fields like psychology and sociology where latent variables are interrelated. This method yields two matrices: the pattern matrix, which shows unique relationships between variables and factors, and the structure matrix, which shows correlations between factors and variables.

This approach provides a more nuanced view of data but increases the complexity of interpretation, as correlated factors need to be considered in relation to each other.

Types of Oblique Rotations

Direct Oblimin: Direct oblimin allows researchers to control the degree of factor correlation by adjusting a parameter known as the delta value. This flexibility makes it a popular choice in fields where factors are expected to correlate.

Promax: Promax first applies an orthogonal rotation, typically varimax, before allowing factors to correlate. It is faster to compute and is commonly used in large datasets where factor correlations are expected.

Comparison of Orthogonal and Oblique Rotations

The choice between orthogonal and oblique rotations depends on the theoretical assumptions and empirical data. Orthogonal methods offer simplicity, but may misrepresent relationships if factors are actually correlated. Oblique methods offer flexibility and a more accurate reflection of data but are harder to interpret.

Orthogonal rotations, like varimax, are suited for independent factors, while oblique methods like promax are ideal when factors are expected to overlap.

Practical Implications and Recommendations

When selecting a rotation method, it’s important to consider the nature of the factors:

For independent factors, orthogonal rotations like varimax provide clear, interpretable results. For correlated factors, oblique methods like direct oblimin or promax are more appropriate as they provide a more nuanced understanding of the relationships between factors, despite being more complex.

Understanding these trade-offs is crucial for producing accurate, interpretable results in factor analysis.