Exactly, we do not care they are different (usually). We care in what way and how much they are different. Then we care about what possible explanations there may be for that difference.<p>I would say an exception is studies of ESP, etc where the existence of any effect would be surprising. However, in practice, everyone just assumes paranormal researchers messed up the experiment somehow. Small effects are not taken seriously even if they are &quot;significant&quot; because there are many explanations for such differences.