Methods » Z-NSUM

Z-NSUM

Network Scale Up Method

The method is efficient in estimating incidence/prevalence of “sensitive” issues, it is capable of estimating the size of subpopulations of unknown size with smaller samples and perhaps with lower costs.

Respondents are asked questions of the type “How many X do you know?”, where X ranges over different subpopulations of both known and unknown size. Respondents do not have to admit to belonging to any particular group, unlike in most other survey methods. “How many X do you know?” questions can easily be integrated into almost any survey.

Hence, the proportion of subjects in E known to any member of T is the same as the proportion of members of E belonging to general population T.

The total number of people known by a respondent, his or her degree of personal network size, is estimated by asking the respondent about the number of contacts he or she has in several subpopulations of known size using the same assumption that an individual should know roughly their degree times the proportion of people in a given subpopulation. The size of the unknown subpopulation is then estimated using responses to questions about the number of people known in the unknown subpopulation combined with the degree estimate, leading to the scale-up estimator.

For more methodological information about the method, please contact us on: info@zetaresearch.eu.