ICT4TS – Exam summary
4
Sample and sampling plan
The set of samples should represent all the population and respect quotas as much
as possible. Some sampling methods:
-
Simple random sample
: pick a random set of samples at the beginning
-
Systematic sampling
: pick the next sample each time
-
Snowball sampling
: each interviewee suggests a next contestant
-
Convenience sample
:
decided by interviewer
-
Quota sampling
: respondents’ characteristics should be distributed as in society
-
Stratified sample
: respondents are organized to belong to a certain group
-
Cluster sampling
: a systematic sampling inside a stratified population
Data protection
Data is protected by the GDPR (General Data Protection Regulation of the EU), which
implies that:
-
Right to know by advance the nature of the questions
-
Right to access to information and rectification for respondents
-
Right to know the recipients of the survey
Travel surveys typologies
-
On flows
: passengers passing through a section of the road (through cable that
goes
through the street, or other counters)
-
On narrow areas
: A closed are selected and the inwards and outwards flow is
considered, in clue neighbors is done like near a shopping center or downtown.
-
On screen lines
: Lines divide a city in two zones, and the flow between the zones
is studied. Rivers are natural screen lines because they facilitate the work. They
can be used also in closed lines.
-
On wide areas
: wide areas are regions, or nations. Travelers than are influenced
by the intervention to be done, in the plan area, are stopped (a sample of them)
and a questionnaire is applied (2%-4% of the Universe).
-
On parking:
People stopped in a parking
is interviewed asking O-D, purpose,
costs
of parking and trip, and used modes. This is useful for setting political costs
to cars.
Other ways to classify them
-
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