This invention relates to a method and a system for generating a quantitative measure reflecting the severity of a medical condition. A receiver unit receives biosignal data collected from a population of patients having varying degrees of the medical condition. A processor uses the biosignal data for determining reference feature values for each respective patient within the population, where the determining being made in accordance to a pre-defined set of reference features. The processor then assigns each respective patient within the population of patients with a reference feature vector having as vector elements the reference feature values associated with the patient. The processor also uses the reference feature vectors of the patients as input in determining combinations of features describing the variance in the data, where the size of the combinations is an indicator for the severity of the medical condition. This invention further relates to a method and a system for using the quantitative measure for determining a success indicator for a probe compound by implementing the quantitative measure, where a receiver unit receives biosignal data collected from a test subject posterior to administering the probe compound to the test subject, and a processor determines an analogous feature vector as determined for the population of patients. Finally, the processor determines the scalar product between the feature vector determined for the test subject and the combinations of features describing the variance in the data. This scalar product is the success indicator telling how successful the probe compound is.