In order to test the effectiveness of the debate of the candidates for the president, researchers randomly contacted 1000 people on the phone. An attempt was made to contact all 1000 one day before the debate and ask their voting intentions. Only 910 were actually reached by phone; 80 out of the 910 people refused to participate. One day after the debate, 810 of the 910 people were reached and again asked their voting intentions. In addition they were asked if they had seen the debate on television. The before-after change of the viewers and non-viewers were compared to conclude which candidate was more effective in the debate. What kind of experimental design is being used? Describe relevant potential extraneous variables in this experiment. Can this experiment design rule out these extraneous variables?

This chance, however, is only about 1 in 154,000 for a typical Pew Research Center survey. ... Telephone numbers for Pew Research Center polls are generated through a ... The key to survey research is to have a random sample so that every type of ... Why don't your surveys ever reflect the opinions of people I know?

answer; (73%);

the historians cited in the article all agree with one another about the cause of the civil war. despite coming from different backgrounds and cultures, the historians agree that slavery was the root cause of the civil war. the fact that all these historiansgenerally agree with one another makes their shared viewpoints more reliable and valid, especially because the historians have different backgrounds and all work for the well-respected institutions of howard university, clemson university, and the university of colorado.