The "line of best fit" between two variables is the regression line.Regression lines are written in the form \(y = a + bx\), where \(x\) is the independent variable and \(y\) is the dependent variable.For a positive correlation, \(b\) will be positive.For a negative correlation, \(b\) will be negative.Interpolation means to make predictions using the regression line for the dependent variable that are within the range of the data. This is reliable because you can be confident that the trend will be linear within the range of the data.Extrapolation means to make predictions using the regression line for the dependent variable that are outside the range of the data. This is unreliable because you cannot be confident that the trend will continue in the same linear manner beyond the range of the data.