The GP STD acquisition function leverages the uncertainty estimate provided by GPs to guide the AL process. In the context of GPs, each prediction for a given input 𝑥 is accompanied by a mean estimate 𝑓(𝑥) and a standard deviation 𝜎(𝑥), which reflects the model's confidence in that prediction . The GP STD acquisition function is defined directly by this predictive uncertainty as seen in equation 2: