<prompt> Translate the following text to EnglishUchunguzi wa kesi mara nyingi hutumia mfano mmoja au wachache tu, kwa sababu kukusanya na kuchambua data kamili ni ngumu sana kwa idadi kubwa ya tovuti.  <response>: Case studies often use one or only a few instances, because collecting and analyzing comprehensive data are prohibitively difficult for large numbers of sites. 