Shannon Entropy

A measure of the average uncertainty or unpredictability associated with a set of possible outcomes, defined by Claude Shannon as H = -Σ p(x) log₂ p(x), where p(x) is the probability of each outcome. In the context of interface evaluation, entropy quantifies how much uncertainty exists about which command a user intends to perform before any input action is observed. Higher entropy means more possible commands with similar probabilities, requiring more information to be transmitted to identify the intended command. Shannon entropy is measured in bits and provides a theoretical upper bound on how efficiently an interface can communicate user intentions.