Stratified Sampling

Definition

Stratified sampling is a method of sampling that involves dividing a population into smaller groups, known as strata, based on shared characteristics, and then selecting samples from each stratum. This technique ensures that different segments of the population are adequately represented in the sample, enhancing the accuracy and reliability of survey and observational research findings.

5 Must Know Facts For Your Next Test

1. Stratified sampling helps reduce sampling bias by ensuring all subgroups are represented according to their proportion in the population.
2. The selection of strata can be based on various characteristics such as age, gender, income level, or education, depending on the research goals.
3. Stratified sampling can be done proportionately, where samples are drawn from each stratum in proportion to their size in the population, or disproportionately, for special emphasis on certain groups.
4. This method is particularly useful in research where differences among subgroups may influence results, making it vital for studies focused on diverse populations.
5. Using stratified sampling can increase the precision of estimates compared to simple random sampling, especially when there are significant differences between strata.

Review Questions

• How does stratified sampling improve the reliability of survey results?
  • Stratified sampling enhances the reliability of survey results by ensuring that various subgroups within a population are represented. By dividing the population into strata based on key characteristics and then sampling from each stratum, researchers can capture more nuanced data that reflects the diversity within the population. This approach minimizes bias and provides a more accurate reflection of the entire group’s opinions or behaviors.
• In what situations might a researcher prefer using disproportionate stratified sampling instead of proportionate stratified sampling?
  • A researcher might choose disproportionate stratified sampling when they want to ensure sufficient representation of smaller subgroups that may not be adequately represented in a proportionate sample. For example, if a study aims to investigate the opinions of a minority group within a larger population, using disproportionate stratified sampling allows for selecting a larger sample from that specific group to gain insights that might otherwise be lost in a proportionate approach. This method helps highlight unique perspectives or issues faced by these subgroups.
• Evaluate how stratified sampling can affect the validity of conclusions drawn from observational research studies.
  • Stratified sampling significantly enhances the validity of conclusions in observational research studies by ensuring comprehensive representation across different segments of the population. When researchers implement this method correctly, they can draw more accurate conclusions regarding trends and behaviors specific to distinct strata. However, if strata are not chosen carefully or if some are under-sampled or over-sampled, it could lead to skewed data and unreliable conclusions. Therefore, understanding the nuances within each stratum and how they relate to broader patterns is essential for making valid generalizations from the research findings.

Related terms

Population: The entire group of individuals or instances that researchers are interested in studying.

Sampling Frame: A list or database containing all the elements of the population from which a sample is drawn.

Random Sampling: A sampling technique where each member of the population has an equal chance of being selected, ensuring unbiased representation.