<prompt> Translate the following text to EnglishKujua msingi ambao kesi za kesi zilichaguliwa, kwa mfano, ni muhimu katika mkusanyiko; vinginevyo haiwezekani kujua ikiwa kesi bora, kesi mbaya zaidi, kawaida, au kesi kama hizo zinaunganishwa.  <response>: Knowing the basis on which the case instances were selected, for example, is crucial in cumulation; otherwise it is not possible to know whether best case, worst case, typical, or the like instances are being aggregated. 