A Level Biology Practice Exam

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What does stratified sampling involve?

Sampling the entire population without subgrouping
Dividing populations into sub-groups and sampling from each
Collecting data randomly from one single group
Taking samples from the top of varying populations

The correct answer is: Dividing populations into sub-groups and sampling from each

Stratified sampling involves dividing a population into distinct sub-groups, known as strata, based on specific characteristics relevant to the research question. This method ensures that each subgroup is adequately represented in the overall sample, therefore reducing bias and increasing the validity and reliability of the results. For instance, if researchers were studying the dietary habits of high school students, they might stratify the population by grade level, ensuring that each grade is represented in the sample. This approach allows for more precise comparisons and insights regarding the various strata within the population, leading to conclusions that better reflect the diversity present in the entire group.