Research Methods: Sample Populations
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Questions and Answers

What is the primary purpose of using probability-based sampling in research studies?

  • To ensure equal chances of selection for all individuals in the source population (correct)
  • To focus exclusively on specific subgroups of a population
  • To reduce the overall sample size required for the study
  • To include only the most willing participants

    • Which sampling method involves selecting every $10^{th}$ or $100^{th}$ individual from a list?

  • Stratified random sampling
  • Simple random sampling
  • Systematic sampling (correct)
  • Cluster sampling

    • What type of bias is present when individuals in the source population do not have an equal chance of being selected for a study?

  • Random sampling bias
  • Measurement bias
  • Non-random-sampling bias (correct)
  • Sampling bias

    • In stratified random sampling, what is done before selection occurs?

    <p>The source population is divided into groups based on a characteristic</p> Signup and view all the answers

    What is cluster sampling commonly based on?

    <p>Naturally occurring groups within the population</p> Signup and view all the answers

    What is generalizability in research commonly referred to as?

    <p>External validity</p> Signup and view all the answers

    Why must convenience sampling be used with caution?

    <p>It can introduce systematic differences from the intended populations.</p> Signup and view all the answers

    Which method combines snowball sampling with a mathematical model for weighting the sample?

    <p>Respondent-driven sampling</p> Signup and view all the answers

    What is defined as a convenience population?

    <p>A nonprobability-based population selected for its ease of access.</p> Signup and view all the answers

    What does generalizability allow researchers to do with their findings?

    <p>Apply results to a broader target population.</p> Signup and view all the answers

    Why is it essential to include vulnerable populations in research studies?

    <p>It addresses health issues specific to those populations.</p> Signup and view all the answers

    What is a key aspect of community-based participatory research (CBPR)?

    <p>Community members actively participate in all stages of the research.</p> Signup and view all the answers

    What is a negative consequence of recruiting too few participants in a research study?

    <p>The findings may not be representative.</p> Signup and view all the answers

    What is the role of community leaders in the research process?

    <p>They help establish connections but do not replace individual consent.</p> Signup and view all the answers

    What factor is critical in determining the appropriate sample size for a research study?

    <p>Meeting a threshold adequate to answer the research question.</p> Signup and view all the answers

    What is a Type 1 error in statistical testing?

    <p>Finding a significant result when none exists</p> Signup and view all the answers

    Which statement best describes Type 2 error?

    <p>It happens when a research study incorrectly concludes that a treatment has no effect when it actually does.</p> Signup and view all the answers

    How can researchers minimize the likelihood of Type 2 errors?

    <p>By utilizing a larger sample size</p> Signup and view all the answers

    What is the relationship between Type 2 error rate (β) and statistical power?

    <p>Power increases as β decreases.</p> Signup and view all the answers

    Why do sample size estimates typically refer to the study population instead of the sample population?

    <p>To account for participants who decline to be involved.</p> Signup and view all the answers

    What is the primary purpose of determining an appropriate sample size in a quantitative study?

    <p>To estimate the number of participants needed to achieve a desired level of certainty.</p> Signup and view all the answers

    Which of the following statements about confidence intervals is true?

    <p>Confidence intervals represent a range of likely values based on study data.</p> Signup and view all the answers

    What is the impact of larger sample sizes on confidence intervals?

    <p>They reduce the width of confidence intervals.</p> Signup and view all the answers

    How is 'power' defined in the context of statistical tests?

    <p>The chance of correctly rejecting a false null hypothesis.</p> Signup and view all the answers

    Which factor is important when using a sample size calculator?

    <p>Assumptions about the expected characteristics of the sample population.</p> Signup and view all the answers

    If the level of certainty about the inputs is low, what is the recommended course of action regarding sample size?

    <p>Err on the side of a larger sample size.</p> Signup and view all the answers

    Which of the following is not a consequence of larger sample sizes in statistical studies?

    <p>Reduction in data variability.</p> Signup and view all the answers

    What is the formula for calculating power in statistical analysis?

    <p>Power = 1 - β</p> Signup and view all the answers

    Study Notes

    Sample Populations

    • A sample population is a subset of a source population who are invited to participate in a research project.
    • Probability-based sampling is used when a sample population is representative of the source population.
    • Non-random-sampling bias occurs when each individual does not have an equal chance of being selected for the sample population.

    Probability-Based Sampling

    • Simple random sampling: Every person has an equal probability of being selected.
    • Systematic sampling: Individuals are selected from a list or inventory, for example, every 10th or 100th person.
    • Stratified random sampling: The population is divided into groups based on a characteristic before selection.
    • Cluster sampling: A sample is divided into clusters, typically based on naturally-occurring groups.

    Study Populations

    • Study population: Eligible members of the sample population who consent to participate in the study and complete required study activities

    Generalizability

    • Generalizability refers to the applicability of study findings to a broader population.
    • Also known as "external validity" or "representativeness."

    Convenience Samples

    • Convenience populations are nonprobability-based source populations selected due to ease of access.
    • Convenience sampling must be used with caution as results may not be representative of the target population.

    Non-Probability Sampling

    • Chain/snowball/referral sampling: Participants are encouraged to invite others to participate.
    • Respondent-driven sampling: Combines "snowball sampling" with a mathematical model to weight the sample.

    Community Involvement

    • Community-based participatory research (CBPR): Partnerships in which community members identify research priorities and are involved in every stage of the research process.

    Importance of Sample Size

    • Recruiting too many participants: Wastes resources.
    • Recruiting too few participants: Makes the study invalid.
    • Sample size and certainty levels: The desired sample size is based on statistical estimations about how many data points are required to answer the study question with a specified level of certainty.

    Mean

    • The mean is the average value of a variable, calculated by adding up all values and dividing by the total number of individuals.

    Confidence Interval

    • A confidence interval is a statistical estimate of the range of likely values of a parameter in a source population based on the value of that statistic in a study population.

    Sample Size Estimation

    • Sample size calculators: Tools used to identify an appropriate number of participants for a quantitative study.
    • Power estimation: The ability of a statistical test to detect significant differences between subgroups of a population when differences really do exist.

    Type 1 and Type 2 Errors

    • Type 1 (alpha) error: A statistically significant test result is obtained when no significant difference or association actually exists.
    • Type 2 (beta) error: A statistically insignificant test result is obtained when a significant difference or association actually exists.

    Refining the Study Approach

    • If the estimated number of available participants is not sufficient, the study approach may need to be rethought.
    • The number of people sampled for a study must be larger than the required number of participants because the participation rate is unlikely to be 100%.

    Next Class

    • October 23, 2024
    • Topics: Questionnaire Development, Surveys/Questionnaires, Collecting Quantitative Data
    • Chapters 21, 22

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    HE 201 Data Collection & Sampling (October 21, 2024) PDF

    Description

    This quiz covers essential concepts related to sample populations and probability-based sampling methods. You will explore different sampling techniques including simple random sampling, systematic sampling, stratified random sampling, and cluster sampling. Test your understanding of biases and the study population involved in research.

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