The article "Correlation: Relationship Between Two Quantitative Variables" discusses how to analyze data in biological research using statistical methods like t-tests, ANOVA, and regression models. It also covers advanced techniques like generalised linear models and classification and regression trees. The authors provide case examples, datasets, and R code to help readers understand and apply these methods. The goal is to help students, researchers, and professionals improve their statistical practice. The book is accessible and useful for anyone interested in analyzing data in biology.