<P> One of the criticisms of opinion polls is that societal assumptions that opinions between which there is no logical link are "correlated attitudes" can push people with one opinion into a group that forces them to pretend to have a supposedly linked but actually unrelated opinion . That, in turn, may cause people who have the first opinion to claim on polls that they have the second opinion without having it, causing opinion polls to become part of self - fulfilling prophecy problems . It have been suggested that attempts to counteract unethical opinions by condemning supposedly linked opinions may favor the groups that promote the actually unethical opinions by forcing people with supposedly linked opinions into them by ostracism elsewhere in society making such efforts counterproductive, that not being sent between groups that assume ulterior motives from each other and not being allowed to express consistent critical thought anywhere may create psychological stress because humans are sapient, and that discussion spaces free from assumptions of ulterior motives behind specific opinions should be created . In this context, rejection of the assumption that opinion polls show actual links between opinions is considered important . </P> <P> Another source of error is the use of samples that are not representative of the population as a consequence of the methodology used, as was the experience of The Literary Digest in 1936 . For example, telephone sampling has a built - in error because in many times and places, those with telephones have generally been richer than those without . </P> <P> In some places many people have only mobile telephones . Because pollsters cannot use automated dialing machines to call mobile phones in the United States (because the phone's owner may be charged for taking a call), these individuals are typically excluded from polling samples . There is concern that, if the subset of the population without cell phones differs markedly from the rest of the population, these differences can skew the results of the poll . </P> <P> Polling organizations have developed many weighting techniques to help overcome these deficiencies, with varying degrees of success . Studies of mobile phone users by the Pew Research Center in the US, in 2007, concluded that "cell - only respondents are different from landline respondents in important ways, (but) they were neither numerous enough nor different enough on the questions we examined to produce a significant change in overall general population survey estimates when included with the landline samples and weighted according to US Census parameters on basic demographic characteristics ." </P>

Compared to when they were first used one of the key problems with telephone polls is the
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