By contrast, researchers in health sciences are frequently faced with the desire to measure something which has not been approached previously—arthritic pain, return to function of post-MI patients, speech difficulties of aphasic stroke patients, or clinical competence of junior medical students. The difficulties and questions raised in developing such instruments range from the straight-forward (e.g.’how many boxes do I put on the response?’) to the complex (e.g.’How do I establish whether the thing is measuring what I hope it is?’). Nevertheless, to a large degree, the answers are known, although frequently difficult to access.