Research methodology for the Internet: external validity (generalizability)

The burgeoning use of the Internet for nursing research calls for a need to examine characteristics of electronic populations, and how they can be conceptualized relative to their physically based counterparts. The 1963 work of Campbell and Stanley, now 40 years old, is revisited in relation to external validity, and its applicability to today's world of quantitative and qualitative research. Internal and external differences in Internet populations are outlined, and a new threat to external validity is proposed: the threat of Networked Effects, which is composed of 4 subfactors: Co-occurring Interferences to Testing, Self-selection Mechanisms, Electronic Group Environments, and Cultural Differences. These Internet threats must be well understood when formulating research methodology.