In 1997, this strategy was re-evaluated and in 1998 ISER modified its methods to include more random numbers from small exchanges. This aimed to improve and calculate the probability that all households in Alaska with telephones would have a chance of inclusion in the study. Disproportionate stratified random sampling is a variation of cluster sampling. These values are determined by analyzing all possible 100 blocks for an area. Because Alaska has such a low number of active residential lines, Alaska requires a large amount of phone sample each month to operate successfully.
Participation is random, anonymous and confidential.
Respondents are randomly selected from among the adult members of the household. Only those living in households are surveyed. Data Collection Interviews are conducted by trained college interns. The interviews arre conducted primarily in the evenings and on weekends, during the two weeks of every month specified by the CDC for all states. Monthly data files are sent to the Centers for Disease Control and Prevention.