Behavioural Surveillance Surveys - The Wisdom of Whores

Of the two methods, the preferred
procedure is the “segmentation” method, as
this method comes the closest to approximating
a conventional two-stage cluster sample, and
is thus less prone to bias. However, sketch
mapping is required to use the method, and
thus it may not be feasible in all settings.
In such instances, the modified random walk
method provides a suitable alternative,
low-cost method, provided that a measure
of size is obtained for sample clusters.
Non-response in household surveys
One of the problems faced in all household
surveys is that of what to do when respondents
chosen for a survey are not available to
be interviewed. In some surveys, fieldworkers
are instructed to substitute other respondents
(e.g., in the neighboring household) for
respondents who have been chosen for a
survey but cannot be readily located. For
sub-population surveys, this practice should be
discouraged because of the potential bias that
may be introduced by only interviewing
readily accessible respondents. For example,
youth who engage in high-risk behaviors may
be more likely to live in one-person households
and/or to be at home less regularly,
thus making it more difficult to locate them
for a survey interview. However, if such
persons are systematically excluded from
sub-population surveys because they are
difficult to locate, sub-population survey data
will be biased toward under-estimating the
extent of risky behaviors.
The recommended course of action is to
require at least three return visits (“call-backs”)
to each sample household in order to obtain
an interview from each eligible respondent
in the original sample of households.
In scheduling return visits, information should
be sought from other household residents and
neighbors in order to determine the best times
to find difficult-to-locate individuals at home.
If after three attempts it is still not possible to
obtain an interview, the case should be dropped
and not replaced by a substitute respondent.
To compensate for the possible loss of sample
size, it is recommended that the target sample
size for household surveys be increased by
10% or so.
School surveys of youth
When undertaking household surveys of
youth is not feasible (or desirable), an
alternative strategy for tracking behaviors of
youth is to undertake non-household surveys
of different segments or sub-groups of youth.
In settings where a sizable proportion of
youth remain in school at the secondary level,
conducting surveys in schools represents a
fairly cost-effective way of reaching youth
15-19 years of age for data collection purposes.
Two cluster sampling schemes for undertaking
school surveys are described below - the first
for use where the survey can be conducted
in school classrooms using self-administered
questionnaires, and the second where data
collection has to take place outside of
classroom settings.
B EHAV I OR A L S U R V EI L L A NC E SURV EY S APPEN DI X 3
329