Sampling in Research: Population, Types, and Errors
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Sampling in Research: Population, Types, and Errors

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Questions and Answers

What is the primary goal of scientific research?

To describe the nature of a population

What is the main reason why a census is not possible to conduct every time?

Time and resource constraints

What is a sample in the context of research?

A subset of the population that is representative of the entire population

What are the three factors that affect sample representation?

<p>Sampling procedure, sample size, and participation rate</p> Signup and view all the answers

What is the relationship between sample size and accuracy of results?

<p>The larger the sample size, the more accurate the results</p> Signup and view all the answers

What is a sampling frame?

<p>A list of population elements from which a sample will be drawn</p> Signup and view all the answers

What is a characteristic of probability sampling?

<p>Each target population element's chance for selection is known</p> Signup and view all the answers

What is the main difference between probability and non-probability sampling?

<p>Probability sampling is based on mathematical guidelines, while non-probability sampling is not</p> Signup and view all the answers

What is the primary purpose of using stratified sampling in research?

<p>To ensure that the sample is representative of the entire population</p> Signup and view all the answers

What is the characteristic of the population within each subset in stratified sampling?

<p>Homogeneous within each subset</p> Signup and view all the answers

What is the difference between proportionate and disproportionate stratified sampling?

<p>Proportionate sampling represents each stratum in proportion to the population, while disproportionate sampling over-represents a particular stratum</p> Signup and view all the answers

What is the purpose of dividing the population into mutually exclusive and exhaustive subsets in stratified sampling?

<p>To create a simple random sample from each group</p> Signup and view all the answers

What type of sampling is used when the population within each subset is homogeneous, but heterogeneous between subsets?

<p>Stratified sampling</p> Signup and view all the answers

What is the characteristic of the strata in proportionate stratified sampling?

<p>Each stratum is represented in proportion to the population</p> Signup and view all the answers

What is the advantage of using stratified sampling in research?

<p>It ensures that the sample is representative of the entire population</p> Signup and view all the answers

What is the main advantage of using probability sampling?

<p>It allows researchers to make generalizable inferences about the population</p> Signup and view all the answers

What is the purpose of stratified sampling in relation to key variables?

<p>To ensure that the sample is representative with respect to key variables</p> Signup and view all the answers

Which type of sampling relies on personal judgment in the element selection process?

<p>Non-probability sampling</p> Signup and view all the answers

What is the main difference between probability and non-probability sampling?

<p>Probability sampling allows for the estimation of sampling error, while non-probability sampling does not</p> Signup and view all the answers

Which type of probability sampling involves dividing the population into subgroups and randomly selecting elements from each subgroup?

<p>Stratified sampling</p> Signup and view all the answers

What is the main advantage of simple random sampling?

<p>Each element in the population has an equal chance of being selected</p> Signup and view all the answers

What is the main disadvantage of non-probability sampling?

<p>Results are not generalizable to the population</p> Signup and view all the answers

What is the main difference between systematic and cluster sampling?

<p>Systematic sampling involves selecting every nth element, while cluster sampling involves selecting clusters of elements</p> Signup and view all the answers

Which type of non-probability sampling involves selecting participants based on their availability and convenience?

<p>Convenience sampling</p> Signup and view all the answers

What is a characteristic of systematic error?

<p>Consistently produces incorrect results in the same direction</p> Signup and view all the answers

What type of error occurs when an individual provides an inaccurate response to an item?

<p>Response error</p> Signup and view all the answers

What is the primary cause of non-coverage error?

<p>Failure to include some units or entire sections of the target population in the sampling frame</p> Signup and view all the answers

What is a type of non-response error?

<p>Refusal to participate</p> Signup and view all the answers

What can be done to reduce non-coverage error?

<p>Recognize its existence and work to improve the sampling frame</p> Signup and view all the answers

What is a possible cause of response error?

<p>Lack of respondent's willingness to provide the true answer</p> Signup and view all the answers

What type of error is predictable?

<p>Systematic error</p> Signup and view all the answers

What is the main difference between response error and non-response error?

<p>Response error occurs when respondents provide inaccurate responses, while non-response error occurs when respondents refuse to participate</p> Signup and view all the answers

When is a non-probability sample preferred?

<p>When the research is a pilot study</p> Signup and view all the answers

What is the primary concern in preliminary studies or pilot studies?

<p>Researchers' experience</p> Signup and view all the answers

What is more important in sample selection?

<p>Sample quality</p> Signup and view all the answers

What is the primary purpose of a sample?

<p>To represent the entire population</p> Signup and view all the answers

Which type of sampling method is most suitable for research projects that require high levels of precision?

<p>Probability sampling</p> Signup and view all the answers

What is the main limitation of a large unrepresentative sample?

<p>It is not representative of the population</p> Signup and view all the answers

What is the primary advantage of a probability sample?

<p>It is more representative of the population</p> Signup and view all the answers

Which of the following is a characteristic of a sample?

<p>It is a subset of the population</p> Signup and view all the answers

Study Notes

Population and Sample

  • A population is a group or class of subjects, variables, concepts, or phenomena.
  • The goal of scientific research is to describe the nature of a population.
  • A census is the process of examining every member of a population, but it is not possible to conduct a census every time due to time and resource constraints.
  • A sample is a subset of the population that is representative of the entire population.
  • Sample representation is directly affected by three factors: sampling procedure, sample size, and participation rate.
  • If a sample is sufficiently large and representative of the population, the results from a study using the sample can be generalized to the population.

Types of Sampling Procedures

  • There are two broad types of sampling methods: probability and non-probability sampling.
  • Probability sampling:
    • A sample that is selected according to mathematical guidelines.
    • Each target population element's chance for selection is known.
    • Allows researchers to calculate the amount of sampling error and make inferences about the population.
    • Types of probability sampling: simple random, systematic, stratified, and cluster.
  • Non-probability sampling:
    • A sample that relies on personal judgment in the element selection process.
    • Neither sampling error nor the margin of sampling error can be estimated or calculated.
    • Inferences are limited to the sample.
    • Types of non-probability sampling: convenience, judgment, snowball, and quota.

Probability Sampling Methods

  • Simple random sampling: each subject, element, event, or unit in the population has an equal chance of being selected.
  • Stratified sampling:
    • The population is divided into mutually exclusive and exhaustive subsets.
    • A simple random sample of elements is chosen independently from each group/subset.
    • Used when researchers wish to ensure that a specific subsample is adequately represented.
  • Systematic sampling: consistently produces incorrect results in the same direction, therefore predictable.

Research Error

  • Research error can be classified into two types: sampling error and non-sampling error.
  • Sampling error: occurs when the sample is not representative of the population.
  • Non-sampling error: occurs when the data is not accurate or reliable.
  • Systematic error: consistently produces incorrect results in the same direction, therefore predictable.
  • Non-response error: occurs when an individual fails to provide information or responds inaccurately.
  • Response error: occurs when an individual provides inaccurate information due to various reasons.

Sample Size

  • The sample size depends on the research design, the amount of acceptable error, time constraints, and the quality of data required.
  • Generally, the larger the sample, the better, but a large unrepresentative sample is as meaningless as a small unrepresentative sample.
  • Sample quality is more important than mere size.
  • Factors to consider when determining sample size: research design, amount of acceptable error, time constraints, and the quality of data required.

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Description

This lecture covers the basics of sampling in research, including the difference between population and sample, types of sampling procedures, and research error. It also discusses sample size and its importance.

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