All solutions here are SUGGESTED. Mr. Teng will hold no liability for any errors. Comments are entirely personal opinions.
Order the list of 10000 regular customers, then randomly select a number from 1 to 20, e.g. 4. Then select the 4th, 24th, 44th, 64th, … customers on the list until all 500 customers are surveyed.
1. Sample is evenly spread out over the list of customers.
1. Not representative as the list could exhibit periodic or cyclic pattern.
2. Biased as the list could exhibit periodic or cyclic pattern.
Students, please go memorise how to describe these methods and know how to write in context. We MUST write in context of the question.