Element selection techniques play a crucial role in
determining how individual elements or units are chosen from the population to
form a sample. Here are some common element selection techniques used in
sampling:
1. Unrestricted Sampling:
§ In unrestricted sampling, each element in the
population has an equal chance of being selected for the sample. This approach
is commonly used in simple random sampling, where every element is selected
independently of other elements.
2. Restricted Sampling:
§ Restricted sampling involves imposing certain
restrictions or conditions on the selection of sample elements. This can
include stratification, clustering, or other criteria that guide the selection
process. Restricted sampling techniques include:
§ Stratified Sampling: The population is divided into
homogeneous subgroups (strata), and samples are selected from each stratum to
ensure representation of different characteristics.
§ Cluster Sampling: The population is divided into
clusters, and a random sample of clusters is selected for inclusion in the
study.
§ Systematic Sampling: Elements are selected at
regular intervals from a list or sequence, following a predetermined pattern.
3. Judgement Sampling:
§ In judgement sampling, the researcher's judgment or
expertise is used to select sample elements that are deemed representative of
the population. This technique is subjective and relies on the researcher's
knowledge and experience to identify relevant elements for inclusion in the
sample.
4. Quota Sampling:
§ Quota sampling involves setting quotas for different
subgroups of the population based on certain characteristics. Interviewers are
then tasked with filling these quotas by selecting individuals who meet the
specified criteria. Quota sampling is a non-probability sampling technique that
allows for control over the composition of the sample.
5. Convenience Sampling:
§ Convenience sampling involves selecting sample
elements based on their ease of access or availability to the researcher. This
technique is often used when time and resources are limited, but it may
introduce bias if the selected elements do not adequately represent the
population.
6. Snowball Sampling:
§ Snowball sampling is a technique where existing
participants in the study recruit new participants from their social networks.
This method is commonly used in studies where the target population is hard to
reach or identify initially, such as in studies of marginalized or hidden
populations.
By understanding and selecting appropriate element
selection techniques based on the research objectives, population
characteristics, and sampling constraints, researchers can ensure the validity,
representativeness, and reliability of their sample designs. Each technique has
its advantages and limitations, and researchers should carefully consider the
implications of their choices on the quality of the study results.
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