The art of deducing information about large data and frequently challenging population from the analysis of a smaller sample is a the foundation of statical reasoning in the vast field of data analysis and research. This practice is referred to as “Sampling“. For any type of market research study, probability sampling is a method of choosing samples from a large population. The theory behind this is to randomly select a sample for the purpose of survey research. Stratified Sampling and Cluster Sampling are the two type of probability sampling.
Stratified and Cluster Sampling are statistical sampling techniques used to efficiently gather data from large populations. Stratified sampling divides the population into distinct subgroups based on characteristics or variables, ensuring homogeneity and variation. A random sample is selected from each stratum, reducing potential bias and ensuring accurate estimates. Cluster sampling divides the population into naturally occurring groups, such as geographical regions or organizational units, and randomly selects clusters to capture variability within them.
Both stratified and cluster sampling have several benefits, but they also have some drawbacks. We will see the difference between them in brief in this article.
What is Stratified Sampling ?
Stratified sampling divides a population into distinct and homogenous divisions, or strata. The categorization is based on certain characteristics or important factors. Stratified sampling divides the population into different subgroups or strata based on particular characteristics or criteria. Due to the strata’s design, individuals within each subgroup are more homogeneous, however certain subgroups are different. Then, based on size or significance, a random sample is taken from each stratum.
Advantages of Stratified Sampling:
- Improved Representativeness: Stratified sampling makes sure that each strata or subgroup within the population is fairly represented in the sample. It leads to more accurate reflection of population’s diversity and traits.
- Reduced sampling error: It reduces variability within each stratum by segmenting population into homogenous strata. Less variability reduces sampling error and estimations are more accurate.
- Effective subgroup analysis: It facilitates in-depth analysis of these subgroups, as they are fairly represented in the sample.
- Increased Precision: It typically produces estimates compared to simple random sampling. When working with limited resources and requirements for the precise results, this precision is especially beneficial.
What is Cluster Sampling?
Cluster sampling is a statistical sampling approach that divides a vast population into naturally occurring groups called clusters before collecting data from each cluster. These clusters, which are subsets of the population that are representative of it, can be geographical areas, organizational units, or any other logical groupings. Instead than choosing specific elements, researchers choose a small number of clusters at random and include all of the items found in those clusters in the sample. When it is more possible and affordable to gather data from clusters rather than individuals, this strategy is especially helpful. It helps in capturing the variation within clusters as well.
Advantages of Cluster Sampling:
- Simple Sampling Design: Cluster sampling simplifies the sampling process by grouping elements into clusters which makes it easier to manage and collect data from small clusters.
- Cost and Resource Efficiency: It is more cost effective than other methods because it reduces the logistical and operational expenses associated with reaching dispersed individuals.
- Practical for Large Populations: With large number of population, Cluster sampling allow researchers to efficiently collect data from selected clusters reducing time and effort.
- Facilitates Access: When in some situations individual elements are difficult to access, cluster sampling helps researchers to reach clusters that are more accessible.
Difference Between Stratified and Cluster Sampling
Cluster sampling and stratified sampling are two different statistical sampling techniques, each with a unique methodology and aim. Let’s see how they differ from each other.
|
Parameters |
Stratified Sampling |
Cluster Sampling |
|---|---|---|
|
Definition |
Stratified sampling divides a population into homogeneous strata based on variables of interest. A random sample is selected from each stratum proportionally, ensuring each subgroup is adequately represented in the final sample, reducing potential bias and allowing for more precise estimates. |
Cluster sampling is a statistical technique that divides a population into naturally occurring groups, such as geographical regions or organizational units. Researchers randomly select clusters and include all elements within them in the sample, reducing costs and logistical challenges. This method provides insights into variability within selected clusters. |
|
Precision |
It enables more precise estimates within each stratum. |
Precision of cluster sampling may vary within clusters. |
|
Homogeneity |
Stratified sampling has homogeneity within groups. |
Cluster sampling has homogeneity between groups. |
|
Heterogeneity |
In stratified sampling, there can be heterogeneity between the groups or subgroups (called strata). |
Heterogeneity within groups is shown by cluster sampling, allowing for variations among chosen elements. |
|
Groups Formation |
Population divided into homogeneous subgroups known as strata. |
Population divided into naturally occurring clusters. |
| In terms of Cost | Stratified Sampling may involve in higher cost then the Cluster Sampling. | Cluster Sampling is cost effective. |
Similarities Between Stratified and Cluster Sampling
Although cluster sampling and stratified sampling have certain differences, they also have some similarities:-
- Both techniques aim to increase sampling effectiveness by segmenting the population into smaller groups.
- Both approaches take into account population variability.
- Random sampling techniques are used in stratified and cluster sampling.
- When sampling the entire population is not viable or cost-effective, stratified and cluster sampling can also be useful alternatives.
FAQ’S on Stratified and Cluster Sampling
Q1. When to use cluster sampling and when to use stratified sampling?
Answer :
Cluster sampling is appropriate for populations that are geographically distributed, whereas stratified sampling works best for populations that are heterogeneous and have particular variables of interest.
Q2. Which is better stratified or cluster sampling?
Answer :
The decision between stratified sampling and cluster sampling relies on the research goals and the nature of the population being studied. Stratified sampling is beneficial when dealing with diverse populations, while cluster sampling is more suitable for populations spread across different locations. The superiority of one method over the other is subjective and context-dependent.
Q3. Which sampling method is more cost-effective?
Answer :
Cluster sampling is often considered more cost-effective because it minimizes the requirement to individually reach and sample every element. Instead, it concentrates on selected clusters, which helps save time and resources, particularly for populations that are geographically scattered.