Variation in drug responsiveness to a paicular dose of the drug in different individuals can be obtained from:-

ED50 : dose at which 50% of subject will responds to drug. Potency :- Measure of amount of drug necessary to produce an effect of a given magnitude. Efficacy: Magnitude of response a drug can cause when it interacts with a receptor. Depends on of drug receptor complex formed. * In this Quantal DRC, x-axis represents the log dose and y-axis represents the percentage of population responding.* It is used when responses are like all or none. The middle point of curve when projected to x-axis gives effective dose and lethal dose in 50% of population.