With the invention of online research in the 1990s the multiple site entry technique became possible, because the recruitment of participants via different links (URLs) is very easy to implement.
[4] This means, a unique string of characters is appended to the URL for each recruitment source, e.g. “...index.html?source=studentlist” for a list of students.
[1][2] The multiple site entry technique helps to detect potential sampling problems, which in turn ensures the quality and generalizability in the data collection over the Internet.
[6][3] The multiple site entry technique has already been applied successfully in different research areas.
For instance, Holbrook and Lavrakas[7] discussed the multiple site entry technique in the field of experimental survey research.