Table of ContentsView AllTable of ContentsWhy Use SamplesProbability SamplesNonprobability SamplesSampling Errors
Table of ContentsView All
View All
Table of Contents
Why Use Samples
Probability Samples
Nonprobability Samples
Sampling Errors
Close
In statistics, a sample is a subset of a population that is used to represent the entire group as a whole. When doing psychology research, it is often impractical tosurveyevery member of a particular population because the number of people is simply too large. To make inferences about the characteristics of a population, psychology researchers use arandom sample.
Keep reading to learn about how samples are used in psychology research, the different types of samples, and the errors that may occur when using samples.
Why Psychology Researchers Use Samples
When researching an aspect of the human mind or human behavior, psychology researchers can rarely collect data from every single affected individual. Instead, they use a smaller sample of individuals to represent the larger group.
The goal when choosing a sample is to make sure it represents the entire group accurately. This means that the sample should reflect the diverse characteristics present in the total population. The sample must accurately represent the population in question so researchers can generalize their results to the larger group withstatistical analysis.
In psychological research and other types ofsocial science research, experimenters typically rely on a few different sampling methods. These can be grouped into probability and nonprobability samples.
Types of Probability Samples
Probability sampling means every individual in a population stands a chance of being selected. Because probability sampling usesrandom selection, every subset of the population has an equal chance of being represented in the sample.
Probability samples are more representative of large populations and researchers are better able to generalize their results to the group as a whole when they use probability samples.
Simple Random Sampling
Stratified Random Sampling
Stratified random sampling involves separating the population into subgroups and then taking a simple random sample from each of these subgroups. For example, researchers may divide the population into subgroups based on race, sex, or age, and then take a simple random sample of each of these groups.
Stratified random sampling often provides greater statistical accuracy than simple random sampling because it ensures each of the subgroups is accurately represented in the sample.
Cluster Sampling
Cluster sampling involves dividing a population into smaller clusters, often based on geographic location. A random sample of these clusters is then selected, and all of the subjects within the cluster are measured.
For example, imagine you are doing a study on school principals in your state. Collecting data from every single school principal would be cost-prohibitive and time-consuming. But, if you were to use a cluster sampling method, you would randomly select five counties from your state and then collect data from every subject in each of those five counties to create a representative sample.
RecapProbability sampling methods allow psychology researchers to get a more representative sample. Techniques that might be used include simple random sampling, stratified random sampling, and cluster sampling.
Recap
Probability sampling methods allow psychology researchers to get a more representative sample. Techniques that might be used include simple random sampling, stratified random sampling, and cluster sampling.
Introduction to Research Methods in Psychology
Types of Nonprobability Samples
Nonprobability sampling involves selecting participants using methods that do not give every subset of a population an equal chance of being represented. For example, a study may recruit participants from an already established group of volunteers.
One problem with this type of sample is that volunteers might differ from non-volunteers on certain variables, which can make it difficult to generalize the results to the entire population.
Convenience Sampling
Convenience sampling involves selecting participants for a study based on what is most convenient–people who are easily accessible and have the time. If you have ever volunteered for a psychology study conducted through your university’s psychology department, then you have participated in a study that relied on a convenience sample.
Studies that rely on asking for volunteers or using clinical samples available to the researcher are also examples of convenience samples.
How Snowball Sampling Used in Psychology Research
Purposive Sampling
Purposive sampling involves seeking out individuals who meet certain criteria. For example, a researcher might be interested in learning how college graduates between the ages of 20 and 35 feel about a topic. In purposive sampling, the researcher might conduct telephone interviews to intentionally seek out people who meet their criteria.
Quota Sampling
Instead, they establish criteria to assign each subgroup a certain percentage of the sample. This differs from stratified sampling because, to find individuals within each subgroup, researchers use non-random methods to fill the quotas for each subgroup.
RecapNonprobability sampling can also be used when selecting a sample in psychology research. Such methods are less representative of the general population. Techniques include convenience sampling, purposive sampling, and quota sampling.
Nonprobability sampling can also be used when selecting a sample in psychology research. Such methods are less representative of the general population. Techniques include convenience sampling, purposive sampling, and quota sampling.
How to Conduct a Psychology Experiment
Sampling errors are differences between what is present in a population and what is present in a sample. Because sampling cannot include every single individual in a population, errors can occur. This can ultimately have an impact on the results of psychology research.
In general, the larger the sample size, the smaller the level of error.This is simply because the closer the sample is to the size of the total population, the more likely it is to accurately capture all of the characteristics of the population.
Summary
Samples are important in psychology research because they allow scientists to study what is happening in a larger population without having to reach every individual in the entire group.
Different types of samples can be used depending on what researchers are studying and the resources they have available to collect data. Probability samples tend to be more representative of the larger group. Nonprobability samples, on the other hand, tend to involve selecting participants based on availability and studying specific subsets of a larger group, which is less representative of the larger group.
Sampling errors can occur, however, with any type of sampling. To minimize errors, researchers strive to use large, representative samples.
What Is Reliability in Psychology?
2 Sources
Verywell Mind uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
Valliant R, Dever J.Estimating propensity adjustments for volunteer web surveys.Sociol Methods Res. 2011;40(1):105-137. doi:10.1177/0049124110392533
Goodwin CJ.Research In Psychology: Methods and Design, 12th ed. John Wiley and Sons.
Meet Our Review Board
Share Feedback
Was this page helpful?Thanks for your feedback!What is your feedback?HelpfulReport an ErrorOtherSubmit
Was this page helpful?
Thanks for your feedback!
What is your feedback?HelpfulReport an ErrorOtherSubmit
What is your feedback?
