Analyzing a Regression Using Data from a Sub-Sample of the Current

Essay

Analyzing a regression using data from a sub-sample of the Current Population Survey with about 4,000 observations,you realize that the regression R2,and the adjusted R2, 2,are almost identical.Why is that the case? In your textbook,you were told that the regression R2 will almost always increase when you add an explanatory variable,but that the adjusted measure does not have to increase with such an addition.Can this still be true?