ABSTRACT
This chapter considers air traffic control in certain circumstances and most have been employed at some time, but measures that are inappropriate for the objectives are wasteful and can mislead. The efficacy of measurement is crucially dependent on the correct choice of measures and tools. Different kinds of measure are required for different kinds of objective. Time and event recording is a well-established form of measurement. To be valid, such measures must be totally passive in that the processes of measurement must not interfere in any way with the activity to which they are applied. A perennial problem in the measurement of task performance is the inclusion of the controller's mental processes where these have no immediate counterpart as recordable events. The consequences of inconsistency depend on its nature, on the measures affected, on the measurement objectives, and on the context of measurement. Social factors can be measured through beliefs, attitudes and opinions, for which standard measurement techniques have evolved.
