In signal detection theory, what is a decision variable?

Question

Quizplus · Accepted Answer

The Answer is In signal detection theory, a decision variable is a quantitative measure that reflects the evidence for the presence of a signal amidst noise. It is the internal response of a sensory system to a stimulus, which can be influenced by both the actual stimulus (signal) and random fluctuations or background information (noise).

The decision variable is used to make a judgment about whether a signal is present or not. It is essentially a criterion that the observer sets, either consciously or unconsciously, to determine whether the sensory input exceeds a certain threshold that indicates the presence of a signal. If the decision variable exceeds this threshold, the observer decides that the signal is present; if it does not, the observer decides that the signal is absent.

The concept of the decision variable is central to signal detection theory because it allows for the quantification of the observer's performance in detecting signals. It also accounts for the fact that detection is not perfect and is influenced by both the sensitivity of the observer to the signal and the observer's bias or tendency to respond in a particular way under conditions of uncertainty.

By analyzing the decision variable in relation to the threshold, researchers can derive measures such as the hit rate (the rate at which signals are correctly detected) and the false alarm rate (the rate at which noise is incorrectly identified as a signal). These measures can then be used to calculate the observer's sensitivity (d') and criterion (c), which are key parameters in signal detection theory that describe the observer's ability to discriminate signal from noise and their decision bias, respectively.

In Signal Detection Theory, What Is a Decision Variable