Podcast
Questions and Answers
Why is sampling considered statistically sound in research?
Why is sampling considered statistically sound in research?
What is the key to success in sampling methods?
What is the key to success in sampling methods?
Why might using a census instead of a sample not be feasible?
Why might using a census instead of a sample not be feasible?
In surveys, how is determination of whether a participant belongs to the Population of Interest (POI) typically done?
In surveys, how is determination of whether a participant belongs to the Population of Interest (POI) typically done?
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Why might it be impossible to conduct a full census?
Why might it be impossible to conduct a full census?
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What does step two in sampling methods involve?
What does step two in sampling methods involve?
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What is the purpose of identifying a sampling frame in a research study?
What is the purpose of identifying a sampling frame in a research study?
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Which type of sampling is used when the population has subgroups or segments to ensure each are represented?
Which type of sampling is used when the population has subgroups or segments to ensure each are represented?
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In which type of sampling are samples selected based on using people who are easily accessible?
In which type of sampling are samples selected based on using people who are easily accessible?
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What method is used in systematic sampling to select respondents?
What method is used in systematic sampling to select respondents?
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What is the main assumption underlying cluster sampling?
What is the main assumption underlying cluster sampling?
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Which type of sampling can create distortions in the total sample due to oversampling of specific groups?
Which type of sampling can create distortions in the total sample due to oversampling of specific groups?
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When is convenience sampling typically used?
When is convenience sampling typically used?
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Which type of sampling involves establishing quotas for population subgroups based on demographic factors?
Which type of sampling involves establishing quotas for population subgroups based on demographic factors?
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What is the key difference between cluster sampling and stratified sampling?
What is the key difference between cluster sampling and stratified sampling?
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What is the main advantage of systematic random sampling over other methods?
What is the main advantage of systematic random sampling over other methods?
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Why is sampling considered statistically sound in research?
Why is sampling considered statistically sound in research?
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What is the key to success in the sampling process?
What is the key to success in the sampling process?
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Why might using a census instead of a sample not be feasible?
Why might using a census instead of a sample not be feasible?
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What is the first step in the sampling process?
What is the first step in the sampling process?
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What does step two in the sampling process involve?
What does step two in the sampling process involve?
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Why is it important to ensure that the sample is representative of the population?
Why is it important to ensure that the sample is representative of the population?
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What aspect of the sampling frame is highlighted as being ideal?
What aspect of the sampling frame is highlighted as being ideal?
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Which type of sampling involves selecting samples from each subgroup that are proportional to the size of the group?
Which type of sampling involves selecting samples from each subgroup that are proportional to the size of the group?
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What method of sampling is characterized by samples being drawn from separate subgroups?
What method of sampling is characterized by samples being drawn from separate subgroups?
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Which type of sampling is known for being less expensive and faster but lacks the ability to calculate sampling errors?
Which type of sampling is known for being less expensive and faster but lacks the ability to calculate sampling errors?
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What is the key difference between cluster sampling and systematic sampling?
What is the key difference between cluster sampling and systematic sampling?
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Which type of sampling involves selecting samples based on researcher's personal judgment about representativeness?
Which type of sampling involves selecting samples based on researcher's personal judgment about representativeness?
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In which type of sampling does every member of the population have an equal chance of being selected?
In which type of sampling does every member of the population have an equal chance of being selected?
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What is the main assumption underlying cluster sampling?
What is the main assumption underlying cluster sampling?
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Study Notes
The Concept of Sampling
- Sampling refers to the process of obtaining information from a subset (sample) of a larger group (population).
- Sampling is considered statistically sound and can be accurate, even with small samples, if the method of selection ensures the sample is representative of the population.
Why Use Samples Over a Census?
- Not feasible: Population is too large or too widely dispersed.
- Not desirable: Time-consuming, expensive, and increased non-sampling errors.
- Not necessary: A carefully selected sample can accurately reflect the population.
Steps in Sampling
Step One: Define the Population of Interest (POI)
- Often specified in terms of geographics, demographics, product or usage, or awareness measures.
- Determination of whether a participant belongs to a POI is done through screening questions.
Step Two: Choose a Data-Collection Method
- The data-collection method has implications for the sampling process.
- Examples of data-collection methods include using the internet, mail, mall-intercepts, door-to-door, etc.
Step Three: Identify a Sampling Frame
- The sampling frame is the list of the members of the population from which units to be sampled are selected.
- Ideally, the list would be complete, but this is usually not the case.
Types of Sampling
Probability Sampling
- Every member of the population has a known, non-zero chance of selection.
- Sampling errors can be calculated, and survey results can be projected onto the entire population of interest.
Probability Sampling Overview
- Simple random sampling: Every member of the population has an equal chance of being selected.
- Stratified sampling: Sample from separate groups.
- Systematic sampling: Use every nth person.
- Cluster sampling: Focus on a few groups.
Stratified Sampling
- Used if the population has subgroups or segments to ensure each is represented.
- Samples are drawn from each subgroup.
- 2 types of stratification: Probability Proportional to Size Sample (PPS) and Disproportionate Sampling.
Cluster Sampling
- Often used when there is no adequate sample frame.
- Researcher selects a sample of subgroups and then collects data from all or some of the members.
- Assumption is that the elements in a cluster are as heterogeneous as those in the total population.
Non-Probability Sampling
- Convenience sampling: Samples are selected based on using people who are easily accessible.
- Judgement sampling: Selection criteria are based on the researcher's personal judgment about representativeness of the population under study.
- Quota sampling: Quotas, based on demographic or classification factors, are established for population subgroups.
- Snowball sampling: Used when sample unit characteristics are quite rare or very difficult to find.
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Description
Explore the importance of sampling in research and how to ensure samples are representative of a population. Learn the difference between a sample and a census.
