📖 Glossary · Advanced

Factor Analysis

How factor analysis reveals the hidden dimensions inside a questionnaire—and the sample sizes and pitfalls behind honest results.

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Factor analysis asks how many independent threads a bundle of items really measures. Exploratory (EFA) discovers structure; confirmatory (CFA) tests a claimed structure against data. Loadings show which items belong to which dimension.

🧮 Formula

Correlation matrix → extracted factors (PCA/EFA); fit indices (CFI, RMSEA) for CFA.

✏️ Worked example

An 18-item engagement survey loads cleanly on three factors—voice, growth, energy—so the report scores three dimensions, not one average.

🎯 When to use it

Before naming dimensions in any productized assessment, and whenever alpha is suspiciously low on a supposedly single scale.

⚠️ Watch out

EFA needs ~100+ respondents and 5 items per factor minimum; rotate and interpret theory, not eigenvalues alone.

Questions practitioners ask

EFA or CFA first?

EFA to discover, CFA to confirm—ideally on separate samples. Skipping EFA is guessing; skipping CFA is unproven.

Is PCA the same as EFA?

No—PCA decomposes variance, EFA models latent structure. For questionnaire dimensions, EFA is the honest default.

Turn the concept into a live assessment:Factor Analysis

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Glossary

Likert Scale Cronbach's Alpha Test-Retest Reliability Inter-Rater Reliability ∞