All surveys on people's confidence in "One Country, Two Systems" conducted by the POP Team are telephone surveys conducted by interviewers under close supervision.
All these surveys are conducted by telephone interviewers under close supervision. Target population of these surveys are Cantonese speakers in Hong Kong of age 18 or above.
The sample size of all these surveys are more than 500 successful cases each time. Since May 2000, it has been increased to more than 1000, and weighted according to gender-age distribution of the Hong Kong population.
Starting from mid-January 2014, telephone numbers are randomly generated using known prefixes assigned to telecommunication services providers under the Numbering Plan provided by the Office of the Communications Authority (OFCA). Invalid numbers are then eliminated according to computer and manual dialing records to produce the final sample.
Before mid-January 2014, telephone numbers are first selected randomly from telephone directories as seed numbers. Another set of numbers is then generated by using the plus/minus one/two method. Duplicate numbers are then screened out, and the remaining numbers mixed in a random order to become the final sample.
Upon successful contact being made with a target household, one member of the household is selected among those present using the "next birthday" rule.