Here is correlation matrix on data set:
Assignment was to Regress Onlinepop against PC's, Phones, and Educ and then to regress the predicted values of the dependent variable Onlinepop against the residuals resulting in the following scatterplot in order to detect for heteroskedasticity.
Next based on results of model I was to consider three scenarios. First, triple Education expenditure. Second, double PC's. Third, double Phones. Here are results of model. R square was .98
QUESTION - I don't understand why variable Educ has a negative coefficient. Intuitively, I would expect a positive sign. Can you explain why? Could it be multilcollinearity or is it the heteroskedasticity at work?
See attached file for full problem description.
This shows how to regress the predicted values of a dependent variable against the residuals in order to detect for heteroskedasticity.