Use data from the year 1981 to answer the following questions. The data is for sales that occurred in 1981 in North Andover, Massachusetts. 1981 was the year when construction began on a garbage incinerator. To study the effects of the incinerator location on housing prices, consider the simple regression model:
log(price) = Bo + B1*log(dist)
In this equation, price represents the housing price in dollars and dist represents the distance from the house to the incinerator measured in feet. Interpreting this equation causally, what sign do you expect for B1 if the presence of the incinerator depresses housing prices? Estimate this equation and interpret the results.
To the simple regression model in part (i), add the variables log(intst), log(area), log(land), rooms, baths, and age. In this case, intst represents the distance from the home to the interstate, area represents the square footage of the house, land represents the lot size in square feet, rooms represents the total number of rooms, baths represents the number of bathrooms, and age represents the age of the house in years. Now, what do you conclude about the effects of the incinerator? Explain why and also discuss if there are conflicting results.
Add log(intst) to the model from part (ii). Now, what happens? What do you conclude about the importance of functional form? Is the square of log(dist) significant when you add it to the model from part (iii)?
Use the data in WAGEI for this exercise. Use OLS to estimate the equation:
log(wage) = Bo + B1*edue + B2*exper + B3*sexper + u
Report the results using the usual format. Is exper statistically significant at the 5% level? Using the approximation %Awage = 100*(B1 + 2*B2*exper - B2*exper), find the approximate return to the fifth year of experience. What is the approximate return to the twentieth year of experience? At what value of exper does additional experience actually lower the predicted log(wage)? How many people have more experience in this sample?