An instrument is reliable to the extent that independent, well-trained raters obtain similar results under similar conditions of rating. It is important to note, therefore, that reliability depends on the training and ability of the rater and on the design of the trial, as well as on the characteristics of the instrument. Any method of physically restricting a patient's movement. In the UK this means careful holding of a patient's arms, legs, trunketc. Sampling Identifying a group which is representative of a larger population.
Staff ratios The ratio of staff to patients.
A review in which evidence on a topic has been systematically identified, appraised and summarised according to predetermined criteria. An instrument is valid to the extent that the results obtained by using it are confirmed by results from others and independent methods of measurement which themselves have been well-validated. From Development to Use. Concise Oxford Textbook of Psychiatry.