RESEARCH METHOD COHEN ok

218 SURVEYS AND DEVELOPMENTAL STUDIES
studies), cross-section analysis and trend studies
are summarized in Box 9.4 (see also Rose and
Sullivan 1993: 184–8).
Several of the strengths and weaknesses of
retrospective longitudinal studies share the same
characteristics as those of ex post facto research,
discussed in Chapter 12.
Postal, interview and telephone surveys
Although we introduce some important features
of approaches to data collection here, we advise
readers to consult Chapters 10, 15 and 16 on
Internet-based research, questionnaire design and
interviews respectively.
Postal surveys
Robson (1993) indicates strengths and difficulties
with postal and interview surveys. Postal surveys
can reach a large number of people, gather data
at comparatively low cost and quite quickly, and
can give assurances of confidentiality (Bailey 1994:
148). Similarly they can be completed at the
respondents’ own convenience and in their
preferred surroundings and own time; this will
enable them to check information if necessary
(e.g. personal documents) and think about the
responses. As standardized wording is used, there
is a useful degree of comparability across the
responses, and, as no interviewer is present, there
is no risk of interviewer bias. Further, postal
questionnaires enable widely scattered populations
to be reached.
On the other hand, postal surveys typically
suffer from a poor response rate, and, because
one does not have any information about the
non-respondents, one does not know whether the
sample is representative of the wider population.
Further, respondents may not take the care
required to complete the survey carefully and,
indeed, may misunderstand the questions. There
is no way of checking this. Bailey (1994: 149)
suggests that the very issues that make postal
surveys attractive might also render them less
appealing, for example:
the standardization of wording
the inability to catch anything other than a
verbal response
the lack of control over the environment in
which the survey questionnaire is completed
the lack of control over the order in which the
questions are read and answered
the risk that some questions will not be
answered
the inability to record spontaneous answers
the difficulty in separating non-response from
bad response (the former being where intended
respondents receive the survey but do not reply
to it, and the latter being where intended
recipients do not receive the survey, e.g.
because they have moved house)
the need for simplicity in format as there is
no interviewer present to guide the respondent
through a more complex format.
Interview surveys
Whereas postal surveys are self-administered,
interview surveys are supervised, and, hence
potentially prone to fewer difficulties. Interview
methods of gathering survey data are useful
in that the presence of the interviewer can
help clarify queries from the respondents and
can stimulate the respondent to give full
answers to an on-the-spot supervisor rather
than an anonymous researcher known through
an introductory letter (Robson 1993). Indeed,
there is evidence that face-to-face encounters
improve response rates. Furthermore, as interviews
can be flexible, questioners are able both to
probe and explain more fully (Bailey 1994: 174).
Interviews are also useful when respondents
have problems with reading and writing. Using
non-verbal behaviour to encourage respondents
to participate is also possible. Moreover, with
interviews there are greater opportunities to
control the environment in which the survey is
conducted, particularly in respect of privacy, noise
and external distractions.
The potential for trust and cooperation
between the interviewer and the respondent is