This allows a determination as to whether a valid conclusion can be drawn about the efficacy of the test drug by providing a measure of assay sensitivity for the study; i.e., did any treatment show superiority to placebo. This design also allows comparison of marijuana with a standard therapy cannabis seeds. If an effective standard treatment exists, there are conditions such as chemotherapy-related nausea and vomiting in which it would be unethical to include a placebo control group. On the other hand, in single-dose analgesic studies a placebo group can be incorporated in the design if appropriate provision is made for administration of a "rescue" analgesic if the study medication proves ineffective.