Stratified Sampling
Stratified Sampling - Related Videos
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Stratified Sampling Method
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2023
Sampling is a technique to select a portion (or subset) of the larger population and study that portion (the sample) to gain information about the population. The sampling method ensures that samples are drawn without bias and accurately represent the population. Because measuring the entire population in a study is not practical, researchers use samples to represent the population of interest. To choose a stratified sample, divide the population into groups called strata and then take a...
14:38
Establishment of Microbial Eukaryotic Enrichment Cultures from a Chemically Stratified Antarctic Lake and Assessment of Carbon Fixation Potential
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Cited by 5 •
2012
Microbial eukaryotes are both a source of photosynthetically-derived carbon and top predatory species in permanently ice-covered Antarctic lakes. This report describes an enrichment culture approach to isolate metabolically versatile microbial eukaryotes from the Antarctic lake, Lake Bonney, and assesses inorganic carbon fixation potential using a radioisotope assay for Ribulose-1,5-bisphophate carboxylase oxygenase (RubisCO) activity.
10:44
Sex Stratified Neuronal Cultures to Study Ischemic Cell Death Pathways
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Cited by 7 •
2013
Primary disassociated embryonic hippocampal neuronal cultures are useful for investigating the signaling mechanisms involved in neuron death. Sexing the embryos before the isolation and dissociation of the hippocampus allows the preparation of separate male and female cultures, which enables the researcher to identify and investigate sex-specific cell signaling.
01:29
Classification of Epithelial Tissues: Stratified Epithelium
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2025
Stratified epithelium consists of several stacked layers of cells. They provide the durability to withstand constant physical and chemical attacks. Stratified epithelium is named after the shape of the most apical layer of cells. Stratified squamous epithelium is the most common type found in the human body. In this tissue, the apical cells are squamous, whereas the basal layer contains either columnar or cuboidal cells. The basal cells divide to form new daughter cells, which gradually become...
07:55
An All-in-one Sample Holder for Macromolecular X-ray Crystallography with Minimal Background Scattering
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Cited by 4 •
2019
A novel sample holder for macromolecular X-ray crystallography along with a suitable handling protocol is presented. The system allows crystal growth, crystal soaking and in situ diffraction data collection at both, ambient and cryogenic temperature without the need of any crystal manipulation or mounting.
FAQs
Separating a heterogeneous material into relatively homogeneous strata limits the influence of major differences between subgroups on the combined estimate. Samples selected within each stratum are more comparable with one another, so composition estimates may vary less than those based on an unstructured sample. This is especially useful when location, particle size, composition, or production batch affects chemical measurements.
Proportional allocation assigns sampling effort according to each stratum’s share of the population. Larger groups therefore contribute more observations, while smaller groups remain represented rather than disappearing into the combined sample. This approach can support an overall estimate that reflects the population structure, although the appropriate allocation depends on which subgroups are important to the investigation.
Strata should reflect characteristics that may influence the chemical result or that must be represented in the analysis. Suitable distinctions can include composition, particle size, location, and production batch. Choosing relevant boundaries helps prevent important subgroups from being overlooked and makes comparisons among sampled portions more meaningful for quality control, monitoring, or material analysis.
First, identify the population and divide it into distinct strata using a relevant characteristic. Next, determine how many samples each stratum should contribute, often in proportion to its size. Finally, select units within every stratum by random or systematic procedures and analyze the resulting samples, keeping their stratum identity available for interpreting the combined result.
It is preferable when the material or population is heterogeneous and certain subgroups could be missed by treating everything as a single pool. In chemistry, this may occur across production batches, locations, particle-size classes, or compositional groups. The approach is therefore relevant to environmental monitoring, pharmaceutical testing, quality control, and analysis of complex materials.
The resulting data can support estimates of chemical composition while showing how different subgroups contribute to the overall population. Because every selected stratum is represented, the findings can reveal differences that a combined sample might obscure. These outcomes help researchers evaluate material quality, monitor environmental samples, and assess whether pharmaceutical or production-related populations are adequately characterized.