Dummy variables Hill et al chapter 9
Parameters that vary between observations Assumption MR1 The parameters are the same for all observations. k= the change in E(y t ) when x tk is increased by one unit, and all other variables are held constant
A model of house prices is the value of an additional square foot of living area, and is the value of the land alone This model omits to take account of location
Intercept Dummy Variables
Slope dummy variable
Combined intercept and slope dummy variables
The effect of a university on house prices: model
The effect of a university on house prices: data
The effect of a university on house prices: results
The effect of a university on house prices: conclusions
Qualitative Variables with Several Categories Note that E 0 is excluded. The dummy variable trap
Interpretation of the wage equation
Testing for the existence of qualitative effects H 0 : =0 H 1 : 0, or >0 Test using a t test
Testing the equivalence of two regressions using dummy variables Known as the Chow Test
Testing the equivalence of investment demand in two firms Restricted Equation (No dummies) Unrestricted Equation (Dummy applied to all parameters) F<F c = So the restrictions are not rejected and it is concluded that the equation is the same for both forms
An alternative way of computing SSU in the Chow test Estimate the simplified equation: for each firm separately SSE u = SSE1 + SSE2