computer science

Proxy-based estimating

Proxy-based estimating is a computer 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 Proxy-based estimating rather than just read about it. In short: Proxy-Based Estimating (PROBE) is an estimating process used in the Personal Software Process (PSP) to estimate size and effort. Proxy Based Estimating (PROBE), is the estimation method introduced by Watts Humphrey (of the Software Engineering Institute at Carnegie Mellon University) as part of the Personal Software Process (a discipline that helps individual software engineers monitor, test, and improve their own w…

Key takeaways

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

Reference excerpt

Proxy-Based Estimating (PROBE) is an estimating process used in the Personal Software Process (PSP) to estimate size and effort. Proxy Based Estimating (PROBE), is the estimation method introduced by Watts Humphrey (of the Software Engineering Institute at Carnegie Mellon University) as part of the Personal Software Process (a discipline that helps individual software engineers monitor, test, and improve their own work). PROBE is based on the idea that if an engineer is building a component similar to one they built previously, then it will take about the same effort as it did in the past. In the PROBE method, individual engineers use a database to keep track of the size and effort of all of the work that they do, developing a history of the effort they have put into their past projects, broken into individual components. Each component in the database is assigned a type (“calculation,” “data,” “logic,” etc.) and a size (from “very small” to “very large”). When a new project must be estimated, it is broken down into tasks that correspond to these types and sizes. A formula based on linear regression is used to calculate the estimate for each task. Additional information on PROBE can be found in A Discipline for Software Engineering by Watts Humphrey (Addison Wesley, 1994).

References

See also Estimation in software engineering

External links Proxy Based Estimating: Concept from chambers.com

Worked examples

Example 1 — a first encounter with Proxy-based estimating

Start with the simplest possible case. Write down what Proxy-based estimating claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In computer 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 Proxy-based estimating 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 Proxy-based estimating 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 Proxy-based estimating

In research: Proxy-based estimating appears in computer 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 Proxy-based estimating 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: Proxy-based estimating is common in secondary-school and first-year university syllabi. It links to neighbouring topics Software engineering costs, Software engineering stubs, so understanding it makes those chapters shorter.
In everyday life: Look for Proxy-based estimating 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 Proxy-based estimating in 20 minutes

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

Frequently asked questions

What is Proxy-based estimating in simple terms?

Why does Proxy-based estimating matter?

Because it connects several computer 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 Proxy-based estimating?

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 Proxy-based estimating.