The topics of correlation and linear regression constitute a complex and subtle system of statistical and mathematical ideas whose teaching-learning raises numerous practical and theoretical problems. In this research paper, the patterns of reasoning that students exhibit, under the approach of informal inferences when they face problems of correlation and regression line are identified. To achieve this, activities were implemented in two stages: in the first stage, two problems (one of estimation and other of best-fit line) were applied to be solved using pencil and paper; the second stage incorporates the use of the Fathom software. [For the complete proceedings, see ED629884.]