1. Ch. 12 The Regression Line Slope and intercept: –y-intercept: point where x=0 –slope = r*SDy/SDx –Regression equation: y=slope*x + y-intercept The regression equation can be used to make a prediction of y when x is given.

2. Example #3 from Activity: The Regression Line 1.Calculate the slope 2.Write the equation in point-slope form: y- (average y) = slope(x – (average x)) 3.Solve to find the y-intercept 4.Predict the mpg if weight=4000 lbs. 5.Graph the regression line.

3. Definition of a regression line: –Data could be summarized by many lines. What is special about the regression line is that it has the smallest RMS(error). This is referred to as Least Squares. Interpretation: –Extrapolating beyond the data is questionable, at best. –The y-intercept is a theoretical construct which is not always meaningful.

4. –The slope is always meaningful, as seen in the (*) questions in the activity. Activity: The Regression Line –Work on #1, 2, 4 in pairs.