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of agreement), so that the averages are rightfully calculated
and compared in various ways. Data are quantitative
and continuous, and statistical models are more easily
developed (Le Lay et al., 2008).
Likewise, Gregory and Davis (1993) showed a consid-
erable agreement between their three sample groups of
respondents.
Few environmental studies provide statistical ratio-
nales for selecting the sizes of respondent samples, so that
scientists use a wide variety of sample sizes (Table 18.3).
Stamps (1992) applied a bootstrap procedure on a set
of 200 student answers and indicated that about 25
to 30 respondents are needed to minimise the error
estimate. Therefore, 'large respondent samples would
probably not, in general, be a cost-effective protocol for
person/environment research' (Stamps, 1992, p. 222).
Nevertheless, the assessment of a relative opinion is not
always the objective, notably when the managers may
know the public opinion. When considering an inferen-
tial procedure therefore, the sample size is determined
according to the traditional sampling strategy.
18.3.3 Theselectionofparticipantgroups
Two questions are considered here: Who is surveyed and
how many people? Each time, the answer depends on the
scientific question asked. It may be focused on relative
comparisons (e.g. a given group of actors compared to
another one) or infer the opinion of a sample to an entire
population, which is becoming complex because of the
sample size and question of representativeness.
Several authors believe that there is a general consensus
about landscape values and tastes in a society. Conse-
quently, any scientist, as a member of society, can claim
to represent its values. In the opinion of the philosopher
Carlson (1977), any person who has good judgment and
is conscious of public preferences can predict landscape
evaluation. Therefore, managers can consider themselves
as representatives of public opinion. Such practices may
however be criticized (Wallace, 1974). Kroh and Gimblett
(1992) consider that preferences derive from a framework
of values, beliefs and experiences. Moreover, experiences
accumulated during life partly determine the reactions to
stimuli (Zube and Pitt, 1981). Few experimental studies
focus on the observers' characteristics, but they are signif-
icant. Many variables have an effect upon descriptive and
evaluative responses: (a) personality and socio-economic
attributes (Zube and Pitt, 1981; Carp and Carp, 1982a et
b); (b) profession and experience, in terms of resource
and environmental management (Zube, 1973a; Buhyoff
et al., 1978; Feimer, 1984; Gregory and Davis, 1993); and
(c) familiarity with a particular environment or a type
of environment (Pedersen, 1978; Zube and Pitt, 1981;
Buhyoff et al., 1983).
The observer's characteristics have an influence on
riverscape evaluation (Lee, 1979). The respondents can
be categorised into several groups, based on the nature
of their contact with rivers: contact sports (canoeists),
non-contact activities (anglers and rowers), and remote-
contact river users (walkers and picnickers) (House and
Sangster, 1991; House and Fordham, 1997). However,
the personal characteristics of the observer remain trivial
compared to the environmental effects (Stamps, 1995
and 1999; Nasar and Lin, 2003). Moser (1984) found
no relation between subjects' recreational activity and
their perception of water quality. Swimmers and fisher-
men were not more sensitive than boaters and walkers.
18.4 Applications with
photo-questionnaires
18.4.1 Fromjudgmentassessment to judgment
prediction
In the experiments that were performed, two issues were
considered (Table 18.4):
•
assessing a judgment in experimental conditions: river-
scape with and without wood, riverscape before and after
a restoration action, observed in summer or in winter,
riverscapes ordered on a gradient from water to gravel
dominance, and from a eutrophic to an oligotrophic state.
The scoring is often combined with additional questions,
allowing the respondents to account for their answers.
•
linking the judgment with the structural organisation of
the riverscape, in order to provide perception models that
are potentially used in the decision-making and planning
process.
For each of these issues, we worked on different sets of
individuals depending on the question that was asked:
first, a sample of the local population, in order to
infer their opinions in terms of landscape judgments,
and second a set of water/local actors, to evaluate per-
ception in terms of both the differences and/or the
consensus between the two groups. Most of the time,
it is difficult to survey a sample that is representative
of the population as this is so time consuming that
the problem must be addressed in a comparative way,
with inter-actor comparisons. The survey does not say
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