Internet versus paper‐and‐pencil survey methods in psychological experiments: Equivalence testing of participant responses to health‐related messages

Despite experiments being increasingly conducted over the Internet, few studies have tested whether such experiments yield data equivalent to traditional methods' data. In the current study, data obtained via a traditional sampling method of undergraduate psychology students completing a paper‐and‐pencil survey (N = 107) were compared with data obtained from an Internet‐administered survey to a sample of self‐selected Internet‐users (N = 94). The data examined were from a previous study that had examined the persuasiveness of health‐related messages. To the extent that Internet data would be based on a sample at least as representative as data derived from a traditional student sample, it was expected that the two methodologies would yield equivalent data. Using formal tests of equivalence on persuasion outcomes, hypotheses of equivalence were generally supported. Additionally, the Internet sample was more diverse demographically than the student sample, identifying Internet samples as a valid alternative for future experimental research.