For the record, we _are_ treating people based on exact same observations albeit correlated on much less number of people. However, we make use of some probability, other observational and subjective evidence in order to determine right course of action. I agree with another comment made above regarding &quot;less data is never the answer&quot;. We may make some mistakes with small amount of data but the only way we will ever learn is by making a hypotheses and acting on it. We should tread carefully but not too careful to never step forward.