Podcast
Questions and Answers
What is the primary purpose of a sampling frame?
What is the primary purpose of a sampling frame?
In what situation is the sampling frame identical to the population of interest?
In what situation is the sampling frame identical to the population of interest?
What is the likely consequence of using the telephone directory as a sampling frame for Vancouver residents?
What is the likely consequence of using the telephone directory as a sampling frame for Vancouver residents?
Which of the following statements accurately describes random error?
Which of the following statements accurately describes random error?
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If a researcher selects participants by approaching passersby at a specific location, which source of bias may be introduced?
If a researcher selects participants by approaching passersby at a specific location, which source of bias may be introduced?
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Which sampling design feature is most closely related to representativeness?
Which sampling design feature is most closely related to representativeness?
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What is the effect of using an insufficient sampling frame?
What is the effect of using an insufficient sampling frame?
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Which scenario represents an example of selection bias?
Which scenario represents an example of selection bias?
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What characterizes a good sample in research?
What characterizes a good sample in research?
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What is a disadvantage of using a systematic random sample?
What is a disadvantage of using a systematic random sample?
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Which scenario exemplifies a biased sample?
Which scenario exemplifies a biased sample?
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What type of bias is demonstrated by the city engineer who randomly selects a location on a map?
What type of bias is demonstrated by the city engineer who randomly selects a location on a map?
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In which situation is a stratified random sample most appropriate?
In which situation is a stratified random sample most appropriate?
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What describes a cluster random sample?
What describes a cluster random sample?
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What type of bias occurs when only certain individuals respond to a survey?
What type of bias occurs when only certain individuals respond to a survey?
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What is a characteristic of a judgment sample?
What is a characteristic of a judgment sample?
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What is the potential flaw in using a convenience sample for a study?
What is the potential flaw in using a convenience sample for a study?
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Which of the following elements is NOT a characteristic of a good sample?
Which of the following elements is NOT a characteristic of a good sample?
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When is a simple random sample (SRS) the best choice to use?
When is a simple random sample (SRS) the best choice to use?
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Why is it important to avoid a biased sample when studying a population?
Why is it important to avoid a biased sample when studying a population?
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In which of the following situations is underrepresentation likely to occur?
In which of the following situations is underrepresentation likely to occur?
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What is the primary issue with surveying only a selected group of close friends in a research study?
What is the primary issue with surveying only a selected group of close friends in a research study?
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What can be a consequence of conducting a biased survey in terms of data accuracy?
What can be a consequence of conducting a biased survey in terms of data accuracy?
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What type of bias occurs when individuals with lower GPAs choose not to respond to a survey?
What type of bias occurs when individuals with lower GPAs choose not to respond to a survey?
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Which sampling method ensures that every element has an equal chance of selection?
Which sampling method ensures that every element has an equal chance of selection?
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What condition must be met for response bias to be present in survey results?
What condition must be met for response bias to be present in survey results?
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How does selection bias primarily arise during the sampling process?
How does selection bias primarily arise during the sampling process?
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Which of the following statements is true regarding response bias?
Which of the following statements is true regarding response bias?
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In a survey conducted about GPA, what outcome may indicate non-response bias?
In a survey conducted about GPA, what outcome may indicate non-response bias?
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Which of the following sampling techniques is not a type of random sampling?
Which of the following sampling techniques is not a type of random sampling?
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What best describes a stratified random sample?
What best describes a stratified random sample?
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What is a primary characteristic of systematic random sampling?
What is a primary characteristic of systematic random sampling?
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What is the primary difference between a stratified random sample and a cluster random sample?
What is the primary difference between a stratified random sample and a cluster random sample?
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When is it most appropriate to use a systematic random sample?
When is it most appropriate to use a systematic random sample?
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In the example of selecting 100 elementary school students in Vancouver, what constitutes a cluster?
In the example of selecting 100 elementary school students in Vancouver, what constitutes a cluster?
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What is the role of the stratifying variable in a stratified random sample?
What is the role of the stratifying variable in a stratified random sample?
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How many elements can be sampled using a systematic random sample from a group of 500 members if using a 1-in-10 sampling process?
How many elements can be sampled using a systematic random sample from a group of 500 members if using a 1-in-10 sampling process?
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What must be true about the sampling frame to effectively use a cluster sampling method?
What must be true about the sampling frame to effectively use a cluster sampling method?
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What is the initial step in creating a stratified random sample?
What is the initial step in creating a stratified random sample?
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Which of the following represents a limitation of cluster sampling compared to stratified sampling?
Which of the following represents a limitation of cluster sampling compared to stratified sampling?
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What is a critical consideration when using systematic sampling?
What is a critical consideration when using systematic sampling?
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Study Notes
Sampling and Bias Overview
- A sample is a subset of elements selected from a larger population for data collection.
- The sampling frame is the source from which the sample is drawn, ideally representing the entire population.
- Bias occurs when a sample does not accurately represent the population, while random/sampling error is inherent and non-systematic.
Identifying Key Components
- Population of Interest: The complete group to be studied (e.g., all Vancouver residents).
- Sampling Frame: The actual source used to select samples, may not be identical to the population (e.g., phone directory).
- Sample: The specific individuals selected for the study (e.g., 100 residents approached on the street).
- Parameter of Interest: The characteristic or measurement that will be analyzed (e.g., average spending).
Challenges in Sampling
- When sampling frames do not perfectly match the population, it leads to representational issues.
- Examples of sampling frames include phone directories, registrars lists, or random street surveys.
- Underrepresented groups can skew data, affecting conclusions drawn about the population.
Types of Bias
-
Selection Bias: Occurs when the sample is not representative due to a biased sampling frame or non-random selection methods.
- Example: Surveying only friends underrepresents non-student demographics.
- Non-response Bias: Arises when individuals selected for the sample do not respond, often skewing results.
- Response Bias: Inaccurate responses that systematically favor certain outcomes (e.g., underreporting low GPAs).
Sampling Designs
-
Random Samples: Each element has an equal chance of selection; includes:
- Simple Random Sample (SRS): Every subset of the same size has an equal chance (e.g., lottery).
- Stratified Random Sample: Population divided into strata and SRS conducted in each (e.g., separate samples from individuals and corporate clients).
- Cluster (Multistage) Random Sample: Clusters are randomly selected first; then SRS within clusters is conducted (e.g., surveying one school).
- Systematic Random Sample: Selection follows a fixed interval (e.g., every 10th member).
Cost and Appropriateness of Sampling Designs
- Stratified Random Sample: Most costly; best for populations with diverse characteristics within strata.
- Cluster Random Sample: Least expensive; suitable when clusters share similar characteristics.
- Systematic Random Sample: Useful with sequentially arranged data but avoid cyclical properties with characteristics of interest.
- Simple Random Sample: Often the best choice when other designs are not feasible.
Combining Sampling Designs
- Researchers may employ multiple sampling methods for efficiency, such as combining systematic and stratified designs.
Non-Random Sampling
- Sometimes, researchers rely on non-random methods such as:
- Judgment Samples: Based on the researcher's subjective assessment, aiming for representativity.
- Convenient Samples: Focused on readily accessible subjects, which may introduce biases.
Summary of Bias Sources
- Selection bias can arise from biased sampling frames or non-random selection.
- Non-response bias impacts survey results when there are significant differences between responders and non-responders.
- Response bias influences outcomes based on inaccurate feedback favoring particular responses.
Studying That Suits You
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Description
Test your understanding of sampling methods and bias in data collection with this informative quiz. You will define key concepts related to samples and identify biases that may affect the accuracy of estimates. Gain insights into different sampling designs and their advantages.