several important parameters can be calculated from the dose-response curve. These are the No Observed adverse effect level (NOAEL), which is determined from the bottom of the curve. the maximal effect, and the dose causing a 50 per cent effect or which affects 50 per cent of the animals dosed. this could be a biochemical or pharmacological effect (ED50) a toxic effect (TD50) or a lethai effect (LD50). from these can be determined the tberapeuticindex (TD50/ED50) and the margin of safety (TD1/ED99).