science

Stratification (clinical trials)

Stratification (clinical trials) is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Stratification (clinical trials) rather than just read about it. In short: Stratification of clinical trials is the partitioning of subjects and results by a factor other than the treatment given. Stratification can be used to ensure equal allocation of subgroups of participants to each experimental condition.

Key takeaways

Stratification (clinical trials) belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Stratification (clinical trials) to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Stratification (clinical trials) from memory before moving on to harder problems.

Reference excerpt

Stratification of clinical trials is the partitioning of subjects and results by a factor other than the treatment given. Stratification can be used to ensure equal allocation of subgroups of participants to each experimental condition. This may be done by gender, age, or other demographic factors. Stratification can be used to control for confounding variables (variables other than those the researcher is studying), thereby making it easier for the research to detect and interpret relationships between variables. For example, if doing a study of fitness where age or gender was expected to influence the outcomes, participants could be stratified into groups by the confounding variable. A limitation of this method is that it requires knowledge of what variables need to be controlled.

Types of stratification Stratified random sampling designs divide the population into homogeneous strata, and an appropriate number of participants are chosen at random from each stratum. Proportionate stratified sampling involves selecting participants from each stratum in proportions that match the general population. This method can be used to improve the sample's representation of the population, by ensuring that characteristics (and their proportions) of the study sample reflect the characteristics of the population. Alternatively, disproportionate sampling can be used when the strata being compared differ greatly in size, as this allows for minorities to be sufficiently represented. Stratification is sometimes called blocking, and may be used in randomized block design. Stratified purposive sampling is a type of typical case sampling, and is used to get a sample of cases that are "average", "above average", and "below average" on a particular variable; this approach generates three strata, or levels, each of which is relatively homogeneous, or alike. Stratification is used in quota sampling, a non-random method in which the researcher identifies strata of the population and pre-determines how many participants are needed from each stratum. This is considered a better method than convenience sampling, as it attempts to ensure different strata are properly represented.

See also Stratified sampling Glossary of clinical research

References

Worked examples

Example 1 — a first encounter with Stratification (clinical trials)

Start with the simplest possible case. Write down what Stratification (clinical trials) claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Stratification (clinical trials) before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Stratification (clinical trials) ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Stratification (clinical trials)

In research: Stratification (clinical trials) appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Stratification (clinical trials) in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Stratification (clinical trials) is common in secondary-school and first-year university syllabi. It links to neighbouring topics Clinical trials, so understanding it makes those chapters shorter.
In everyday life: Look for Stratification (clinical trials) outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Stratification (clinical trials) in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Stratification (clinical trials) means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Stratification (clinical trials) out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Stratification (clinical trials) in simple terms?

Why does Stratification (clinical trials) matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Stratification (clinical trials)?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Stratification (clinical trials).