<prompt> Variation in drug responsiveness to a paicular dose of the drug in different individuals can be obtained fromQuantal Dose Response CurveEfficacyPotencyGraded Dose Response Curve  <response>: Drug response to the same drug used in same doses in a population varies based on many factors governing pharmacodynamic variability like age, genetics, co- morbid condition, concomitant medication, etc operant in that subset of population under study. This pharmacodynamic variability in a population is analyzed using a Quantal Dose Response Curve Quantal Dose Response relationship is an all or none plot traced based on response elicited to varying dose of drug administered to a population. Therapeutic Index of a drug is determined based on data plots from Quantal Dose Response Curves. Median Effective Dose ED50 is the dose of a drug required to produce a specified effect in 50 of the population. In preclinical studies, the Median Lethal Dose LD50 is determined in experimental animals - the dose that produced moality of 50 of animal group used in testing. Therapeutic Index is determined as a ratio of LD50ED50 - provides the safety margin of a drug. The wider the Lethal DRC is spaced away from the Therapeutic effect DRC -- Drug has a wide safety margin. Ref:- Goodman Gilmans Pharmacological basis of Therapeutics 13th Ed; Pg Num:- 36 