ABSTRACT
THEAIMinthischapteristoexplaininfairlygeneraltermstheprinciplesunderlyingsamplingtheory.Wedonotattemptto presentthetheoryitselfinrigorousterms,toderiveformulaeor
tobringinalltherefinementsofwhichthesampledesignershould beaware.1Infact,wehaveinmindlesstheneedsofthesample designerthanthoseofthestudentorresearchworkerwhowantsto knowsomethingaboutbasicprinciples.
