13.3. A regression analysis for the 100th Congress predicted the proportion of each representative’s votes on abortion issues that took the “pro-choice” position.6 The prediction equation was

ˆy = 0.350 + 0.011id + 0.094r + 0.005nw + 0.005inc

+0.063s − 0.167p, where r = religion (1 for non-Catholics), s = sex (1 for women), p = political party (1 for Democrats), id = ideology is the member’s ADA score (ranging from 0 at most conservative to 100 at most liberal), nw = nonwhite is the percentage nonwhite of the member’s district, and inc =

income is the median family income of the member’s district.

(a) Interpret the coefficient for political party.

(b) Using standardized variables, the prediction equation is

ˆzy = 0.83zid+0.21zr+0.18znw+0.05zinc+0.03zs−0.18zp.

Comment on the relative sizes of the partial effects. Interpret the coefficient of ideology.