Patent ID: 7269570

Claim:
A computer-implemented method comprising: identifying a group within an available survey panel including a plurality of members, the group having predetermined characteristics; determining a weight for each of the members, said weight being derived to match the members to demographics of the general public; selecting a first set of members from the group for a first survey; temporarily removing the selected first set of members from the available survey panel; adjusting weights of remaining members of the available survey panel to compensate for the removal of the first set of members from the available survey panel and thereby to make the remaining members of the available survey panel match the demographics; and selecting, with a processor, additional members from the available survey panel for a second survey, selection probabilities of the additional members being respectively proportional to the adjusted weights to compensate for the removal of the first set of members from the available survey panel; wherein the step of selecting, with a processor, additional members includes: determining an interval value that is equal to a summation of the adjusted weights of the remaining members of the available survey panel divided by the number of the additional members to be selected; selecting a random number that is between zero and the interval value; assigning an identification (ID) number to each of the remaining members of the available survey panel; determining a cumulative weight for each of the remaining members of the available survey panel, the cumulative weight of each particular remaining member being determined by a summation of the weight of the particular remaining member and the weights of other remaining members whose ID numbers are smaller than the ID number of the particular remaining member; and choosing the additional members from the remaining members, each of the additional members having a cumulative weight that matches the sum of the random number and an integer multiple of the interval value.