ABSTRACT
When a new assessment method is developed it is customary for there to be an examination of its technical quality before it is used in practice. This is common sense: before using such a tool we need to know how well it works. This is true, in principle, of all fields where measurement and assessment are practised whether they be within the scope of the physical or social sciences. A newly developed electronic balance will need to be calibrated and checked over a period of time to ensure firstly that the calibrations match the standard, and secondly that its performance is maintained over time. Such development and field trials will identify inherent difficulties with the instrument, and go a long way towards pointing out errors which might arise under various conditions. For example, the balance may be insufficiently robust for certain settings. As members of the public we take such developments for granted. We expect such assessment and measurement devices to be tried and tested, and hence accurate and reliable. We do not expect to receive differing results from the same process.
