A scatter diagram (also called scatterplot) is a quick visual method used to display relationships between two interval-ratio variables.
Equations for all straight lines have the same general form:
Y^ = a + b(X)
The best-fitting regression line is that line where the residual sum of squares, or Σe2, is at a minimum. Such a line is called the least squares line, and the technique that produces this line is called the least squares method.
The coefficient of determination (r2) and Pearson’s correlation coefficient (r) measure how well the regression model fits the data. Pearson’s r also measures the strength of the association between the two variables.
The general form of the multiple regression equation involving two independent variables is
Y^ = a + b1(X1) + b2(X2)