<prompt> Translate the following text to EnglishUchaguzi wa tovuti hauwezi kuwa urahisi kwa sababu kawaida generalization inataka, na sampuli ya kusudi inaweza kuwa ya kawaida na mwakilishi wa utofauti na bora na mbaya zaidi kesi; idadi ya kesi inategemea program utofauti tangu generalization kawaida alitaka; data kutegemea vyombo vya kawaida, kuchapishwa hati, na uchunguzi; ripoti ni tofauti katika mandhari, tovuti, chronology, na narration.  <response>: Site selection cannot be convenience because usually generalization wanted, and purposive sample can be typical and representative of diversity and best and worst cases; number of cases depends on program diversity since generalization usually wanted; data rely on common instruments, published documents, and observation; reports are varied in theme, site, chronology, and narration 