On its Web site, Advocates for Self-Government offers the “World’s Smallest Internet Political Quiz,” focusing on the U.S. political spectrum. Using just 10 questions, the quiz identifies a person’s political leanings. As of 2012, almost 20 million people had taken the quiz. In 2007, the Web site reported the following breakdown into the five possible categories: centrist, 33.49%; conservative, 8.88%; libertarian, 32.64%; liberal, 17.09%; and statist (big government), 7.89%. 

a. Do you think these numbers are representative of the U.S. population? Why or why not? 

b. Describe the people most likely to volunteer for this sample. Why might this group be biased in comparison to the overall U.S. population? 

c. The Web site says, “Libertarians support maximum liberty in both personal and economic matters.” Libertarians are not the predominant political group in the United States. Why, then, might libertarians form one of the largest categories of quiz respondents? 

d. This is a huge sample—close to 20 million people. Why is it not enough to have a large sample to conduct a study with high external validity? What would we need to change about this sample to increase external validity?