Best Practices in Exploratory Factor Analysis: Four Recommendations
For Getting the Most From Your Analysis
Anna B. Costello and Jason W. Osborne North Carolina State University
PCA ( principal components analysis) is the default method of extraction in many popular statistical software packages, including SPSS and SAS, which likely contributes to its popularity. However, PCA is not a true method of factor analysis and there is disagreement among statistical theorists about when it should be used, if at all. Some argue for severely restricted use of components analysis in favor of a true factor analysis method ( Bentler & Kano, 1990; Floyd & Widaman, 1995; Ford, MacCallum & Tait, 1986; Gorsuch, 1990; Loehlin, 1990; MacCallum & Tucker, 1991; Mulaik, 1990; Snook & Gorsuch, 1989; Widaman, 1990, 1993). Others disagree, and point out either that there is almost no difference between principal components and factor analysis, or that PCA is preferable ( Arrindell & van der Ende, 1985; Guadagnoli and Velicer, 1988; Schoenmann, 1990; Steiger, 1990; Velicer & Jackson, 1990). We suggest that factor analysis is preferable to principal components analysis. Components analysis is only a data reduction method. It became common decades ago when computers were slow and expensive to use; it was a quicker, cheaper alternative to factor analysis ( Gorsuch, 1990). It is computed without regard to any underlying structure caused by latent variables; components are calculated using all of the variance of the manifest variables, and all of that variance appears in the solution ( Ford et al., 1986). However, researchers rarely collect and analyze data without an a priori idea about how the variables are related ( Floyd & Widaman, 1995). The aim of factor analysis is to reveal any latent variables that cause the underlying factor structure; only shared variance appears in the solution. Principal components analysis does not discriminate between shared and unique variance. When the factors are uncorrelated and communalities are moderate it can produce inflated values of variance accounted for by the components ( Gorsuch, 1997; McArdle, 1990). Since factor analysis only analyzes shared variance, factor analysis should yield the same solution ( all other things being equal) while also avoiding the inflation of estimates of variance accounted for.
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