Factor Analysis (FA), which includes Principal Component Analysis (PCA) and Partial Least Squares (PLS), is more and more employed in academia and industry for various purposes such as spectrometer calibration, process modeling, data mining, quality control, etc. While software offering friendly interfaces have contributed to make this approach extremely popular, FA remains far from being straightforward, and examples of inappropriate use are not rare.

Why do we have more factors than compounds? Can Partial Least Squares deal with non‐linear responses? It is not that easy to find easy to understand answers to such questions in chemometrics textbooks, which frequently give explanations through large doses of mathematics. This paper therefore aims at providing non‐experts in this field a practical understanding of Factor Analysis using simple examples and with as few equations as possible.

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