Question

##The same researchers from the Population Council are continuing their investigation of the focal relationship between GDP per capita and fertility rates across countries. In order to confirm the existence of the focal relationship, they decide to control for countries’ population size. The researchers suspect that larger populations could influence both GDP and birth rates (TFR) (but they hope this is not true, because it could invalidate the focal relationship). The researchers conduct a multivariate regression by adding a measure of population size to the regression equation presented in Equation 1 of Table 1. The results of the second regression equation are presented in Equation 2 of Table 1.

Table 1. OLS Regression Coefficients Representing Influence of Economic Output (GDP) and Control Variables on Total Fertility Rate

	Equation 1	Equation 2	Equation 3
Gross Domestic Product per Capita (x 1000)	-.033 (.000)	-.033 (.000)	-.007 (.141)
Population size		-.0000000784 (.378)	-.0000000773 (.063)
Percentage of Women who can Read			-.043 (.000)
Y-intercept (Constant)	3.36	3.39	6.47
R2	.207	.213	.657

(Significance level in parentheses)

The same researchers from the Population Council are continuing their investigation of the focal relationship between GDP per capita and fertility rates across countries. In order to confirm the existence of the focal relationship, they decide to control for countries’ population size. The researchers suspect that larger populations could influence both GDP and birth rates (TFR) (but they hope this is not true, because it could invalidate the focal relationship). The researchers conduct a multivariate regression by adding a measure of population size to the regression equation presented in Equation 1 of Table 1. The results of the second regression equation are presented in Equation 2 of Table 1.

In the box provided, explain why the researchers are controlling for population size. Specifically, which elaboration strategy is being used? Or, what is the purpose of adding this new variable (population size) to the equation? You may draw a picture on your worksheet. You should not reference any numbers from the equation in your answer to this question.

Table 1. OLS Regression Coefficients Representing Influence of Economic Output (GDP) and Control Variables on Total Fertility Rate

	Equation 1	Equation 2	Equation 3
Gross Domestic Product per Capita (x 1000)	-.033 (.000)	-.033 (.000)	-.007 (.141)
Population size		-.0000000784 (.378)	-.0000000773 (.063)
Percentage of Women who can Read			-.043 (.000)
Y-intercept (Constant)	3.36	3.39	6.47
R2	.207	.213	.657

(Significance level in parentheses)

Question 1 What conclusion should the researcher draw about the focal relationship between GDP per capita and birth rates when comparing Equation 2 to Equation 1? You should clearly referencing the specific numbers that you are using to draw your conclusion.

Answer 1