The Essentials of Statistics 3rd Edition by Joseph Healey

Exercise 2

SOC: A scale measuring support for increases in the national defense budget has been administered to a sample. The respondents have also been asked to indicate how many years of school they have completed and how many years, if any, they served in the military. Take "support" as the dependent variable. Compute the zero-order correlations among the three variables.

a. Compute the partial correlation coefficient for the relationship between support (Y) and years of school (X) while controlling for the effect of years of service (Z). What effect does this have on the bivariate relationship? Is the relationship between support and years of school direct?
b. Compute the partial correlation coefficient for the relationship between support (Y) and years of service (X) while controlling for the effect of years of school (Z). What effect does this have on the bivariate relationship? Is the relationship between support and years of service direct? (Hint: You will need this partial correlation to compute the multiple correlation co-efficient.)
c. Find the unstandardized multiple regression equation with school (X 1 ) and service (X 2 ) as the independent variables. What level of support would be expected in a person with 13 years of school and 15 years of service?
d. Compute beta-weights for each independent variable. Which has the stronger impact on support?
e. Compute the multiple correlation co-efficient (R) and the coefficient of multiple determination (R 2 ). How much of the variance in support is explained by the two independent variables? (Hint: You calculated r 2 y 2.1 in part b of this problem.)
f. Write a paragraph summarizing your conclusions about the relationships among these three variables.