Biostatistics: Sampling Methods

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Questions and Answers

What is the primary purpose of using quota sampling?

  • To reduce the time required for sampling
  • To select a subgroup as a sample that is of great interest to study (correct)
  • To ensure equal representation of all subgroups
  • To determine the relationship between subgroups

What is a disadvantage of quota sampling?

  • It is a costly method
  • It is a time-consuming process
  • It requires a list of population elements
  • Variability and bias cannot be measured or controlled (correct)

What is the main focus of judgmental sampling?

  • To select a large sample size
  • To reduce bias in the sample
  • To study rare characteristics
  • To conduct an in-depth study of the cases (correct)

What is an advantage of judgmental sampling?

<p>It enables the study of rare characteristics (A)</p> Signup and view all the answers

What is the primary method of snowball sampling?

<p>Asking known contacts to find people who would like to participate (A)</p> Signup and view all the answers

What is an advantage of snowball sampling?

<p>It enables the researcher to reach groups that are otherwise hard to reach (A)</p> Signup and view all the answers

When is quota sampling often used?

<p>When there is a limited time (A)</p> Signup and view all the answers

What is a characteristic of non-probability sampling?

<p>The sample is selected based on the researcher's judgment (C)</p> Signup and view all the answers

What is the primary purpose of sampling in research?

<p>To allow for generalizability of the research (C)</p> Signup and view all the answers

Which of the following is a characteristic of a target population?

<p>It is a collection of items that have something in common (A)</p> Signup and view all the answers

What is the correct sequence of steps in the research process?

<p>Planning, study design, data collection, data analysis (C)</p> Signup and view all the answers

What is the primary difference between a population and a sample?

<p>A sample is a subset of the population (D)</p> Signup and view all the answers

What is the purpose of generalizability in research?

<p>To make conclusions about the study population and then the target population (D)</p> Signup and view all the answers

What is a study population?

<p>The specific population from which data are collected (C)</p> Signup and view all the answers

Why is it important to consider the participants or subjects of the study during planning?

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

What is the correct sequence of steps in the data analysis process?

<p>Data processing, data analysis, data presentation, interpretation (A)</p> Signup and view all the answers

What type of error occurs when an interviewer influences a respondent's answer?

<p>Interviewer error (A)</p> Signup and view all the answers

Which of the following is an example of adjustment error?

<p>Weighting the data incorrectly (A)</p> Signup and view all the answers

What is a possible consequence of processing error?

<p>Inaccurate data analysis (B)</p> Signup and view all the answers

What is the primary source of non-sampling error?

<p>Data collection (B)</p> Signup and view all the answers

How can errors be reduced in research?

<p>By using valid research designs (B)</p> Signup and view all the answers

Which type of error occurs when a sample is not drawn properly?

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

What type of error occurs when there is a problem with processing the data?

<p>Processing error (C)</p> Signup and view all the answers

What is the benefit of increasing the sample size?

<p>Reducing errors (C)</p> Signup and view all the answers

What is the main characteristic of systematic error?

<p>It is consistent and repeatable (A)</p> Signup and view all the answers

What is the term for errors that arise from the measurement of each sampling unit?

<p>Measurement error (D)</p> Signup and view all the answers

Which of the following is an example of non-sampling error?

<p>Non-response error (C)</p> Signup and view all the answers

What is the primary cause of random error?

<p>Degree to which sample is not perfectly representative of the population (D)</p> Signup and view all the answers

What is the result of non-response error?

<p>Data that is not representative of the population (D)</p> Signup and view all the answers

What is a characteristic of random error?

<p>Each error offsets the other, hence, they are often of little to no concern (A)</p> Signup and view all the answers

What is the primary characteristic of non-probability sampling?

<p>The researcher selects the sample based on subjective judgment (C)</p> Signup and view all the answers

What is the main advantage of convenience sampling?

<p>It is a cost-effective method (A)</p> Signup and view all the answers

What is a disadvantage of convenience sampling?

<p>Variability and bias cannot be measured or controlled (C)</p> Signup and view all the answers

What is the primary difference between quota sampling and stratified sampling?

<p>Quota sampling uses a convenient procedure to select the final subjects (B)</p> Signup and view all the answers

What is the primary goal of selecting a sample in non-probability sampling?

<p>To select a sample that is most accessible and available for the researcher (C)</p> Signup and view all the answers

What is the main characteristic of quota sampling?

<p>The researcher generates homogenous groups, based on specific qualities and traits, that represents the population (A)</p> Signup and view all the answers

Which type of sampling is used when the researcher cannot travel to every unit to collect the required data?

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

What is a type of non-probability sampling where the samples are selected from the population directly because they are most accessible and available for the researcher?

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

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Study Notes

The Research Process

  • The research process involves several stages, including planning, study design, data collection, data processing, data presentation, data analysis, interpretation, and publication.

Planning a Research

  • Planning a research involves considering the participants/subjects of the study.
  • Population: a complete set of items or subjects which can be studied.
  • Target Population: a collection of items that have something in common for which we wish to draw conclusions at a particular time.
  • Study Population: the specific population from which data are collected.
  • Sample: A subset of the study population.

Sampling

  • Sampling is vital to allow for generalizability of the research.
  • Generalizability is a two-stage process: which allows the researcher to generalize conclusions from the sample to the study population and then from the study population to the target population.
  • Sampling methods can be classified into two types: probability sampling and non-probability sampling.

Non-Probability Sampling

  • Non-probability sampling is a sampling technique in which the researcher selects the sample based on subjective judgment rather than random selection.
  • Not all the members of the population have a chance to participate in the study.
  • Types of non-probability sampling include convenience sampling, quota sampling, judgmental sampling, and snowball sampling.

Convenience Sampling

  • Convenience sampling involves selecting samples from the population directly because they are most accessible and available for the researcher.
  • Advantages: very low cost, extensively used/understood, no need for list of population elements.
  • Disadvantages: variability and bias cannot be measured or controlled, volunteer bias.

Quota Sampling

  • Quota sampling involves generating homogenous groups, based on specific qualities and traits, that represent the population.
  • Percentage composition of each group in the population (similar to stratified sampling) is calculated.
  • Convenient procedure is used to select the final subjects.
  • Advantages: moderate cost, very extensively used/understood, no need for list of population elements, introduces some elements of stratification, representative with regard to known characteristics.
  • Disadvantages: variability and bias cannot be measured or controlled, volunteer bias.

Judgmental Sampling

  • Judgmental sampling involves selecting subjects purposively on the basis of having particular features.
  • Most case studies are done in this manner.
  • Sample size may not be large but an in-depth study of the cases is the main focus.
  • Advantages: moderate cost, commonly used/understood, sample will meet a specific objective, useful for qualitative research, useful for rare characteristics.
  • Disadvantages: bias.

Snowball Sampling

  • Snowball sampling involves the researcher asking other known contacts to find people who would like to participate in the study; i.e., referrals.
  • Enables researcher to reach groups that are otherwise hard to reach.
  • Used in rare events, e.g., when studying rare behaviors in the population.

Error Types

  • Non-sampling error: statistical error that arises from the result of data collection, which causes the data to differ from the true values.
  • Types of non-sampling error include systematic error, random error, non-response error, measurement error, interviewer error, adjustment error, and processing error.

Non-Sampling Error: Systematic Error

  • Systematic error arises when the sample is not drawn properly.
  • Affects the sample of the study and often creates useless data.
  • Usually, the fault of the researcher.
  • Consistent and repeatable.

Non-Sampling Error: Random Error

  • Random error arises from the degree to which the sample is not perfectly representative of the population.
  • Errors that cannot be accounted for and just happen.
  • Not the fault of the researcher.
  • Each error offsets the other, hence, they are often of little to no concern.

Reducing Errors

  • Errors can be eliminated by increasing the sample size or the number of samples.
  • Using valid research designs.
  • Applying statistical corrections.

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