The calculation of regression lines has been excluded from the new A-level spec however students should be able 'interpret regression lines'. This applet allows students to practise drawing a line of best fit and explore it's relationship to vertical deviations, squares (which are minimised in a least-squares regression which is the most common form of regression), the line of best-fit generated through a least squares regression and the mean point.[br][br]The data points can be moved around to provide a new data set or to explore the effect of moving a data point on the calculated metrics.[br][br]This applet can also be used to explore the effect of outliers on a regression model by dragging one data point so it becomes an outlier and then by clicking the outlier button and selecting the point.