Correlation analysis is one of the most frequently applied statistical techniques in educational research because it provides a straightforward way to describe the direction and strength of association between variables such as achievement, attitude, interest, retention, and other learning outcomes. This paper discusses the appropriate use of correlation coefficients in educational research, clarifying the concept of correlation and the meaning of the coefficient of correlation as a unit-free index ranging from −1 to +1. It explains how correlation is used to summarise relationships, support prediction, and guide interpretation of educational data, while emphasising that correlation does not establish cause-and-effect relationships. The paper also outlines key properties of correlation coefficients and differentiates simple (bivariate) correlation from multiple and partial correlations. In addition, it reviews major correlation techniques commonly used in education such as Pearson product moment, Spearman rank-order, Kendall’s tau, point-biserial, and related approaches highlighting that method selection should align with measurement scale, distributional assumptions, and the nature of the relationship (linear or non-linear). Finally, the paper notes extended applications of correlation in educational measurement, including hypothesis testing, comparing correlations, and estimating reliability through test–retest and split-half procedures, thereby strengthening statistical decision-making in educational inquiry. Keywords: Correlation coefficient; Pearson product–moment; Spearman rank-order; Educational measurement; Reliability estimation,