Chapter 8: Q. 13 (page 482)
The news article goes on to say: 鈥淭he theoretical errors do not take into account a margin of additional error resulting from the various practical difficulties in taking any survey of public opinion.鈥 List some of the 鈥減ractical difficulties鈥 that may cause errors in addition to the percentage point margin of error. Pay particular attention to the news article鈥檚 description of the sampling method.
Short Answer
The practical difficulty is " Nonresponse bias is the result of not having data for everybody in the sample ".