The regression line is the "best fit" for the data. It assumes a linear relationship between the dependent and independent variable. The regression line interpolates between the data point and allows you to predict the dependent variable based on a value of the dependent variable.
The regression line data on StatKey give both the slope (b) and the intercept (a). Both are super important.
We will use the correlation r as a measure of how good the fit is.
Let me illustrate how to use StatKey to measure correlation and do "best fit". In the video, I will test the relationship between the period of a mass on a spring and the spring constant of that spring. We have not seen this yet but we will soon. the relationship is