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.
THE POSSIBILITIES for research on the Internet can be very compelling. By using time-honored research principles, the researcher can forge new paths of knowledge to help gain a new understanding of emerging and existing phenomena. However, principles of validity, and the ultimate ability to create inference, must be addressed. In looking at current Internet research, 1,2 it is apparent that work needs to be done to link contemporary topics to enduring principles of validity, particularly references to Campbell and Stanley's 1963 definitive work, Experimental and quasi-experimental designs for research, 3 the “bible of validity.” This article will inform researchers about validity issues for investigations conducted on the Internet, and hopefully, assist in the identification of issues that researchers may need to consider when conducting a study on the Internet.
Although Campbell and Stanley's seminal text 3 has withstood the test of time and is frequently cited in non–Internet-related literature, it was written in a simpler time when networked communications were not the norm. Since the advent of the Internet, however, new issues in validity have emerged. Electronic systems, particularly the World Wide Web, e-mail, electronic newsgroups, and discussion boards, offer new avenues to access information and influence users' attitudes, values, and behaviors. However, these electronic systems present new and unique challenges for the research process, particularly in relation to the physical presence of the researcher.
To bring the concept of validity forward into a fresh understanding, the work of Campbell and Stanley 3 will be used as the backdrop in this article to examine validity issues in Internet research. A systematic analysis of the theory related to the notion of external validity (generalizability), and implications for Internet research methodology will be presented. Threats to generalizability will be explored, as well as other issues in both quantitative and qualitative research processes. As the fundamentals are explained, applicability to Internet situations will be noted, and examples described. By examining the principles of Campbell and Stanley and extending their work to Internet investigations, this article should help those who have questioned the inferences drawn from Internet research to not only understand but also implement strategies that support the validity of such investigations.