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inclusions in the frame. For example, a business number is included on a list with household phone
numbers.
As a final example, consider the case of web surveys. A common way to attract respondents to a
web survey is placing a link to the survey on a populaar web site. Basically, this means that the
researcher has no control over who responds to the questionnaire. Coverage error for web surveys is
related to two different causes (cf. Ramos, Sevedi, & Sweet, 1998). First, it is the respondent who
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has to make contact with the data collection program. In a web survey, this requires access to a
computer and the internet, plus some degree of computer skill. Individuals who lack these are not
covered. In addition, interviewing software is in general not hardware or software independent.
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