Agenda 1.Exam 2 Review 2.Regression a.Prediction b.Polynomial Regression
Prediction One of the objectives of regression was to be able to predict the behavior of the dependent variable. Prediction: Providing estimates of values of the dependent variable by using the explanatory regression equation: OR:
First need to establish that the model is a good model with strong explanatory power. We can only use prediction in the region of the data used in the estimation process. Replace X in the equation with the value for which you want to predict the dependent variable. Prediction (cont.)
Example #1: The regression model: Y = X 1.Is the relationship between X and Y positive or negative? 2.If X is 9, what is y? 3.If X changes one unit, how much does Y change? 4.If X is 0, what is y?
Example #2: Y = X X 2 where X 1 is miles driven, X 2 is no of deliveries and Y is hours of drive time. 1. Predict the total drive time of a driver who needs to make 3 deliveries and travel 70 miles. 2. Predict the total drive time of a drive who still drives 70 miles but now makes 4 deliveries?
Polynomial Regression If the relationship between the dependent and an independent variable is not linear, but curvilinear, then using polynomials may improve the model. Y= 0 + 1 X + 2 X 2 + 3 X m X m X1X1 Y X1X1 Y
Polynomial Regression Example The polynomial regression equation is: SALES = ADVERT ADV 2 Predictor Coef Stdev t-ratio p Constant ADVERT ADV R-sq = 95.9% R-sq(adj) = 95.4% Analysis of Variance: SOURCE DF SS MS F p Regression Error Total
Polynomial Regression (cont.) SALES = ADVERT ADV 2 1.Test whether or not the coefficient for ADV 2 is significant. 2.Predict what sales will be when advertising is 7 (in thousands). 3.Predict what sales will be when advertising is 15 (in thousands). 4.Predict what sales will be when advertising is 23 (in thousands).