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?

It enables the study of rare characteristics Signup and view all the answers

What is the primary method of snowball sampling?

Asking known contacts to find people who would like to participate Signup and view all the answers

What is an advantage of snowball sampling?

It enables the researcher to reach groups that are otherwise hard to reach Signup and view all the answers

When is quota sampling often used?

When there is a limited time Signup and view all the answers

What is a characteristic of non-probability sampling?

The sample is selected based on the researcher's judgment Signup and view all the answers

What is the primary purpose of sampling in research?

To allow for generalizability of the research Signup and view all the answers

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

It is a collection of items that have something in common Signup and view all the answers

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

Planning, study design, data collection, data analysis Signup and view all the answers

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

A sample is a subset of the population Signup and view all the answers

What is the purpose of generalizability in research?

To make conclusions about the study population and then the target population Signup and view all the answers

What is a study population?

The specific population from which data are collected Signup and view all the answers

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

To ensure that the sample is representative of the population Signup and view all the answers

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

Data processing, data analysis, data presentation, interpretation Signup and view all the answers

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

Interviewer error Signup and view all the answers

Which of the following is an example of adjustment error?

Weighting the data incorrectly Signup and view all the answers

What is a possible consequence of processing error?

Inaccurate data analysis Signup and view all the answers

What is the primary source of non-sampling error?

Data collection Signup and view all the answers

How can errors be reduced in research?

By using valid research designs Signup and view all the answers

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

Systematic error Signup and view all the answers

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

Processing error Signup and view all the answers

What is the benefit of increasing the sample size?

Reducing errors Signup and view all the answers

What is the main characteristic of systematic error?

It is consistent and repeatable Signup and view all the answers

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

Measurement error Signup and view all the answers

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

Non-response error Signup and view all the answers

What is the primary cause of random error?

Degree to which sample is not perfectly representative of the population Signup and view all the answers

What is the result of non-response error?

Data that is not representative of the population Signup and view all the answers

What is a characteristic of random error?

Each error offsets the other, hence, they are often of little to no concern Signup and view all the answers

What is the primary characteristic of non-probability sampling?

The researcher selects the sample based on subjective judgment Signup and view all the answers

What is the main advantage of convenience sampling?

It is a cost-effective method Signup and view all the answers

What is a disadvantage of convenience sampling?

Variability and bias cannot be measured or controlled Signup and view all the answers

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

Quota sampling uses a convenient procedure to select the final subjects Signup and view all the answers

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

To select a sample that is most accessible and available for the researcher Signup and view all the answers

What is the main characteristic of quota sampling?

The researcher generates homogenous groups, based on specific qualities and traits, that represents the population 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?

Non-probability sampling 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?

Convenience sampling Signup and view all the answers

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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Description

Learn about the steps in conducting scientific research and various methods of sampling data for research in this biostatistics lecture. Also, understand common errors during sampling. Part of BMB 208 course.