stratifikaatiosta

Stratifikaatiosta, or stratification, refers to the process of dividing a population into homogeneous subgroups or strata. These strata are formed based on shared characteristics relevant to the study or survey being conducted. For example, in a public opinion poll, strata might include age groups, income levels, or geographic regions. The primary purpose of stratification is to ensure that each subgroup is adequately represented in a sample, leading to a more accurate and representative outcome.

When conducting stratified sampling, researchers first identify the key strata within the population. Then, a sample is drawn from each stratum independently. The size of the sample taken from each stratum can be proportional to its size in the overall population (proportionate stratification) or it can be allocated in a way that prioritizes certain strata, regardless of their size (disproportionate stratification). Disproportionate stratification is often used when a particular subgroup is of special interest or when there is high variability within that subgroup.

Stratification helps to reduce sampling error and can improve the precision of estimates compared to simple random sampling, especially when there are significant differences between the strata. It is a widely used technique in social sciences, market research, and other fields where understanding diverse population segments is crucial. By ensuring representation, stratification allows for more detailed analysis and more reliable conclusions to be drawn from the collected data.