The BBC internet study: general methodology.

This article provides an overview of a large-scale web-based survey, commissioned by the British Broadcasting Corporation (BBC), designed to investigate sex differences. I describe the background and challenges inherent to Web-based testing, the history and rationale behind this study, the design and implementation, and ethical and methodological considerations in the research design. I also discuss the kinds of data collected from around 255,000 participants, describe basic demographic information about the BBC sample, and examine reliability and validity, both internally and in comparison with other similar studies. I conclude that the dataset was largely reliable, and merits the analyses described later in this special section.