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). Despite these impressive growth rates the penetration of the Internet has not, as yet, developed to the extent that it represents the population as a whole. Taylor (2000) describes the Internet population as being younger and possessing a higher standard of education than the public at large. This may not be as big a problem as it seems, for example in the USA, Internet research tends to focus on doing research aimed at the middle to upper income segment (Mehta and Sivadas, 1995; Oppermann, 1995).

There is, however, a major difficulty relating to the lack of a centralised database of e-mail addresses (Litvin and Kar, 2001). This is in stark contrast to mail surveys where addresses are commonly found in a wide variety of directories and databases. Even where sample frames are available, they frequently become outdated as Internet users change their e-mail providers (Dommeyer and Moriarty, 2000). In a study undertaken by Oppermann (1995) it was discovered that of the 500 e-mail addresses that were selected from the members directory of Association of American Geographers (AAG), 25 per cent were out of date. The advantage to researchers using e-mail (whether to deliver a questionnaire or as an invitation to a Web site survey) is that the error messages are sent back to the sender of the e-mail allowing the researcher (as in the case of Oppermann, 1995) to select another set of individuals from the list in order to attempt to obtain the sample size that the researcher originally envisaged.
Without a centralised e-mail database that covers the whole online population, researchers must use alternative methods to get their samples. Mehta and Sivadas (1995) selected their respondents by initiating a programme that collected the e-mail addresses from individuals that posted discussion articles on the 20 most popular discussion groups within an Internet community known as Usenet, which is basically a world-wide system of discussion groups (Kumar et al., 1999; Jackson and DeComormier, 1999). Although this method was efficient at collecting a large database of e-mail addresses it still may fail to develop a sample that is representative of the population as a whole, it may include the segment that contribute to discussion groups.

Response rates
Another attribute of Internet surveys surrounds the responses from the sample. Most studies agree that when comparing e-mail surveys with mail surveys, response rates can be rapid, in some extremes overnight (Mehta and Sivads, 1995; Tse et al., 1994; Bachmann et al., 2000; Taylor, 2000).

As with normal postal surveys, responses to Internet surveys tend to vary according to the study. However, Table I indicates how various studies have been constructed and how the response rates have differed. It generally appears from the summary in Table I that, with the exception of Parker's (1992) study, response rates from e-mail surveys tend to be lower than those of traditional postal surveys.

A concern brought up by Bachmann et al. (2000) is that, as the population becomes more accustomed to e-mail they may become more reluctant to respond to surveys. Essentially as the “novelty” of the Internet wears off there is the potential that online research may suffer as Internet users become more apathetic towards such studies. Burkeman (2001) has indicated that the volume of e-mails has increased substantially to the point th本论文由英语论文网提供整理，提供论文代写，英语论文代写，代写论文，代写英语论文，代写留学生论文，代写英文论文，留学生论文代写相关核心关键词搜索。