geographical methods (2. how to collect primary data- sampling) Flashcards
what is sampling
sampling is the process of selecting a portion of the population being studied usually to make generalisation about the population (related to hypothesis)
hence the sample is always a subgroup of the population (related to research qn)
why is sampling necessary for fieldwork
because it is often not possible or practice to obtain information from everyone in all places (eg. it may not be practical or even possible to interview every tourist in singapore)
what is the sample size needed for data collected to be reasonable and reliable for analysis
at least 30 or more
what does non probability sampling refer to
a sampling technique where samples are non-randomly (intentionally) selected, often using the researchers copious decision
what does probability sampling refer to
a sampling technique where samples are randomly selected, without the researchers conscious decision
types of non probability sampling
convenience sampling (no grouping) and quota sampling (group)
types of probability sampling
simple random sampling and stratified random sampling
what is convenient sampling about
it is carried out in an ad hoc manner that is most accessible (hence convenient) to the researcher
what is quota sampling about
takes into consideration factors, such as a persons gender, age and ethnicity. these predefined groups/ strata are selected (conveniently) to replicate the general structure of the population, hence it offers good understanding of the population
is there biasness in non probability sampling
yes. researchers may select only respondents from the same age as him/her. this reduces representativeness (reliability) of the data collected
example of quota sampling
a researcher interested in investigating preferences of various green spaces in bedok neighbourhood may select samples based on their gender of singaporeans make or female) using convenience sampling
example of convenience sampling
students working on a project on local transportation may decide to give out a questionnaire survey to the first 100 people outside a twin station on a saturday morning
simple random sampling
normally used when there is little known about the population under study
types of probability sampling
simple random sampling (no goruping) and stratified random sampling (group)
stratified random sampling
used when the population clearly includes significantly different subgroups. the researcher may wish to select a sample that has a proportionate make up to the population based on age or gender (or other categories such as ethnicity)
does not probability sampling methods remove bias
yes. since the description and choice is not made by the researcher, there will be a greater chance of creating a more representative (reliable) data collection
example of simple random sampling
- every member if the population is given a number
- a random number generator (or a
- a dice) is used to generate random miners to select the samples and achieve the sample size
- the researcher may wish to collect samples of air temperature ar different locations of punggol park
- a random number generator is used to pick x and y coordinates which will locate the various points for measurement on a map with grids
example of stratified random sampling
- a researcher may hypothesise that a persons vendor is an important choice of tourist activities
- if 60% of the population is made up of 40% females, the the out must also follow the same ratio
- hence the researcher will have to randomly select 6 males and 4 females if they want a total sample size of 10
-the selection of case by gender in each sub-group should be carried out randomly using a random number generator (otherwise the sampling becomes a quota sampling)
2 good characteristics of a good sampling locations
quantity of respondents and quality of respondents
quantity if respondents
stand at a location where many respondents have to pass through
