This survey was conducted online within the United States by Harris Interactive on behalf of the American Petroleum Institute between April 30 and May 8, 2009 among 1,298 adults (aged 18 and over). Figures for region, age within gender, education, household income and race/ethnicity were weighted where necessary to bring them into line with their actual proportions in the population. Propensity score weighting was also used to adjust for respondents’ propensity to be online.

With a pure probability sample of 1,298, one could say with a ninety-five percent probability that the overall results would have a sampling error of +/- 2.72 percentage points. Sampling error for data based on sub-samples would be higher and may vary. However, that does not take other sources of error into account. This online survey is not based on a probability sample and therefore no theoretical sampling error can be calculated.

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