<prompt> Variation in sensitivity of response to increasing doses of the drug in different individuals can be obtained fromGraded DRCQuantal DRCPotencyEfficacy  <response>: Quantal DRC When the response is an all or none phenomenon e.g. antiemetic drug stopping the vomiting or not, the y-axis response axis shows the number of person responding and X-axis shows the plasma concentration. It thus shows that how many person respond to a paicular dose of the drug. It is used to calculate ED50 and LD50. Median Effective Dose ED50: It is the dose that will produce the desired response in half of the 50recipients. More is ED50, lower is the potency and vice a versa. Median Lethal Dose LD50: It is the dose that will result in death of 50 of the animals receiving the drug. More is LD50, safer is the drug. Therapeutic Index T.I.: It is a measure of the safety of a drug. It is calculated as a ratio of LD50 to ED50. Drugs having high T.I. are safer whereas those having low T.I. are more likely to be toxic. 