science

Rule 48

Rule 48 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 Rule 48 rather than just read about it. In short: Rule 48, also known as Exemptive Relief — Extreme Market Volatility Condition, was a mechanism used by the New York Stock Exchange to ease market opening while volatility is high. It may have the effect of pre-empting trading at disrupted prices, as the designated market makers do not have to disseminate price indications prior to the opening bell.

Key takeaways

Rule 48 belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Rule 48 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Rule 48 from memory before moving on to harder problems.

Reference excerpt

Rule 48, also known as Exemptive Relief — Extreme Market Volatility Condition, was a mechanism used by the New York Stock Exchange to ease market opening while volatility is high. It may have the effect of pre-empting trading at disrupted prices, as the designated market makers do not have to disseminate price indications prior to the opening bell. It was approved in 2007 and repealed in 2016.

History Rule 48 was approved by the U.S. Securities and Exchange Commission on December 6, 2007. It was invoked 77 times from 2008 to September 2015, but only used a few times. For example, it was used on January 22, 2008, and May 20, 2010, as well as September 1, 2015. In the aftermath of disorderly trading on August 24, 2015, the NYSE proposed new rules replacing Rule 48 to handle volatility at market opening. These rules were approved by the SEC in July 2016.

References

Worked examples

Example 1 — a first encounter with Rule 48

Start with the simplest possible case. Write down what Rule 48 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 Rule 48 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 Rule 48 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 Rule 48

In research: Rule 48 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 Rule 48 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: Rule 48 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Finance stubs, New York Stock Exchange, so understanding it makes those chapters shorter.
In everyday life: Look for Rule 48 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 Rule 48 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Rule 48 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 Rule 48 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Rule 48 in simple terms?

Why does Rule 48 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 Rule 48?

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 Rule 48.