A hallmark of a quantal dose-response curve is that it shows:

• A. It shows a population response to different doses
• B. It shows a continuous response in a single patient
• C. It shows a binary yes-or-no outcome across individuals
• D. It shows the time to onset

Answer: (C)

Quantal dose-response curves capture how a population responds in an all-or-none fashion to different doses. At each dose, you look at many individuals and record whether each one exhibits the predefined effect or not. Then you plot the fraction of individuals who respond at that dose. As dose increases, more people reach the threshold and respond, producing a curve that rises from 0 to 1. The essential point is the binary, yes-or-no outcome across individuals at each dose, not the magnitude of response in a single person. This is different from a graded dose-response, where a single subject shows a continuous change in effect, and it’s not about time to onset, which is a separate concept.