If 100% of patients survive with the treatment, vs only 50% without, that's a high survival rate. However, if the treatment only went to 5 patients, it's possi

If 100% of patients survive with the treatment, vs only 50% without, that's a high survival rate. However, if the treatment only went to 5 patients, it's possible that you just happened to get 5 straight patients who would have survived anyway. The probability of that is pretty low (~3%) but you'd need more patients to conclusively prove it.