the relationship between two dependent variables, response rate and the apparent sincerity of
responses to internet questionnaires, were investigated with regard to three independent variables:
whether or not would-be respondents were notified in advance of a coming questionnaire (prenotification),
number of follow-up contacts, and connection time. The sample consisted of 1,400
undergraduates studying at Burapha University in 2007. Research instruments involved an internetbased
questionnaire on the drug addiction problems of young people, and an email letter.