Differential attrition in comparison and experimental groups creates what type of internal invalidity?

Better than 90 percent of incumbent members of Congress who run for reelection are successful. All of the following are contributing factors to this phenomenon, except ________

A) the power of incumbency B) name recognition C) the large number of safe seats D) the franking privilege E) the large number of marginal seats

Hispanics are a demographic group that confuses politicians because they are liberal on some issues and conservative on others. On which of the following issues are Hispanics, as a group, likely to take conservative positions?

a. immigration reform b. health care reform c. middle-class tax relief d. support for same-sex marriage e. antidumping trade regulations