What is the smallest possible stimulus tht an be detected half the time?

The smallest possible stimulus that can be detected half the time is known as the absolute threshold. This threshold varies depending on the type of sensory input (e.g., light, sound, touch) and individual differences. In psychophysics, it is often measured using methods such as the method of limits or the method of constant stimuli. Essentially, it represents the minimum level of stimulus intensity needed for a person to perceive a sensation 50% of the time.