Web surveys - The effect of controlling survey access using PIN numbers

Web surveys generally use some sort of access control to prevent uninvited respondents from taking part in the survey and to prevent multiple completions by the same (invited) respondent. Restriction of survey access can be accomplished in several technically equivalent ways. However, these methods may not be equivalent from a methodological viewpoint. In this article, an exploration of possible effects of access control mechanisms is undertaken. Two different modes of access control were experimentally manipulated. Five hundred respondents were assigned to the automatic login condition. Another 500 respondents were assigned to the manual login condition. It was expected that the automatic login procedure would generate higher response rates but a lower degree of data quality. The results show that using a manual login procedure does not decrease response rates, whereas it does increase the overall degree of data quality.