<prompt> Translate the following text to EnglishUtafiti wa kesi unahusisha kile wataalamu wa mbinu wanaita maarifa mengi, tajiri, kamili ambayo yanapaswa kuja kutoka vyanzo vingi vya data, haswa kutoka kwa uchunguzi wa kwanza.  <response>: Case studies involve what methodologists call thick rich, full information that should come from multiple data sources, particularly from firsthand observations. 