From past to present: understanding the impact of sampling bias on data recorded by the portable antiquities scheme

Abstract

This thesis explores the distribution of the data collected by the Portable Antiquities Scheme (PAS), which records archaeological artefacts recovered by members of the public, many of whom are metal detector users. With over 780,000 artefacts recorded onto an online database, it is not surprising that the PAS data have become an essential part of many research projects. However, until now there has been little work on the biases that are inherent in the data, in particular the effect of sampling bias on the distribution of finds. The thesis is grounded in discussions of sampling theory and collection bias, and suggests that bias can enter the archaeological record in seven stages (burial/loss, preservation, survival, exposure, recovery, reporting, and recording). A range of the factors contained within these stages are explored through three study areas (the Isle of Wight, Hampshire, and Northamptonshire). Within each area the distribution of PAS artefacts is first compared to the known distribution of past human activity, and then to a range of physical and man-made landscape features. Six case studies are used to explore specific elements in more detail, to focus the analysis on those factors that have the most impact on the distribution of finds. These statistical and spatial analyses are supported by a survey of metal detecting methods, which uses primary and secondary sources to explore the impact of different attitudes, experience, and techniques on the distribution of finds. This research identifies a series of choices made by collectors, recorders and landowners, that are shown to have most influence over the distribution of PAS finds – these range from ‘where to search’, through ‘what to recover’, to ‘what to report’. This research shows how an understanding of these choices is essential for those wanting to incorporate the PAS data into their research.

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ORCID for Graeme Earl: orcid.org/0000-0001-9077-4605

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