A 20-year fight between pollsters over whether surveys conducted on the phone or over the Internet are best finally has an outcome: Online polls can be "more accurate" because people are more candid responding to a computer than a live voice in many cases.

At a minimum, according to a lengthy Pew Research Center study, for most questions there isn't a big difference in the answers people give on the phone or online. That alone is good news for polling.

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But on questions that are sensitive, Pew found that people are more candid and harsh when answering online and without the perceived pressure of a live interviewer.

"While many of the differences discovered between modes are modest, some are sizable. And many of the differences are consistent with the theory that respondents are more likely to give answers that paint themselves or their communities in a positive light, or less likely to portray themselves negatively, when they are interacting with an interviewer," Pew concluded.

Walking a fine line on the question of which technique is best, Pew added, "there is no way to determine whether the telephone or the Web responses are more accurate, though previous research examining questions for which the true value is known have found that self-administered surveys generally elicit more accurate information than interviewer-administered survey."

Pew tested the polling models in 60 questions and found differences in a good number of cases. For example, people rated political figures differently when interviewed live or online.

"Hillary Clinton's ratings are a good example of this pattern. When asked on the phone, 19 percent of respondents told interviewers they have a 'very unfavorable' opinion of Clinton; that number jumps to 27 percent on the Web," said Pew, without fully explaining why.

Ditto for questions about discrimination. "When asked about discrimination against gays and lesbians, 62 percent of respondents on the phone say they face 'a lot' of discrimination; on the Web, only 48 percent give the same answer. This mode effect appears among both Democrats and Republicans," said Pew.

"Social interaction inherent in a telephone or in-person interview may also exert subtle pressures on respondents that affect how they answer questions. Respondents may feel a need to present themselves in a more positive light to an interviewer, leading to an overstatement of socially desirable behaviors and attitudes and an understatement of opinions and behaviors they fear would elicit disapproval from another person," Pew explained.

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The findings were heralded by one of the country's online polling champions, John Zogby of Zogby Analytics who weekly authors the Obama Report Card that appears Saturdays in Secrets.

Zogby said he started telephone polling in 1984 but changed as people stopped taking calls and as more jumped on the Internet too. "By 2004 we were ready to try using the Internet for our polling — alongside the traditional telephone methods from our call center. We nailed the presidential race nationally within 1 point and got 16 out of 20 states right," he and his research Zeljka Buturovic said in a statement.

"The advantages of online surveys quickly presented themselves: longer surveys, greater range of questions, more flexibility, lower cost. Our clients get results much more quickly — including overseas work where we have had success using mobile to web methodology.