computer science

Graphical Evaluation and Review Technique

Graphical Evaluation and Review Technique 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 Graphical Evaluation and Review Technique rather than just read about it. In short: Graphical Evaluation and Review Technique (GERT) is a network analysis technique used in project management that allows for the probabilistic treatment of both network logic and estimation of activity duration. The technique was first described in 1966 by Dr.

Key takeaways

Graphical Evaluation and Review Technique 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 Graphical Evaluation and Review Technique to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Graphical Evaluation and Review Technique from memory before moving on to harder problems.

Reference excerpt

Graphical Evaluation and Review Technique (GERT) is a network analysis technique used in project management that allows for the probabilistic treatment of both network logic and estimation of activity duration. The technique was first described in 1966 by Dr. Alan B. Pritsker of Purdue University and WW Happ. Compared to other techniques, GERT is only rarely used in complex systems. Nevertheless, the GERT approach addresses the majority of the limitations associated with PERT/CPM technique. GERT allows loops between tasks. The fundamental drawback associated with the GERT technique is the complex programme (Monte Carlo simulation) required to model the GERT system. Development in GERT includes Q-GERTS - allowing the user to consider queuing within the system.

General GERT rules GERT uses activity-on-arrow notation only. That means that each activity is described on arrow. The nodes are used to connect activities, but also to determine type and conditions of relations between them. Each task has two parameters: duration and probability of appearance. There are three logical operators in GERT which concern activities incoming to the node:

XOR - alternative (only one path possible) OR - alternative (one or more paths can be performed) AND - all paths have to be performed The most common is AND, which means that every incoming activity has to happen before the outcoming one start. There are also two types of relations that concern activities outcoming from the node:

deterministic - every outcoming activity has probability equal to 1, which means that everyone will be performed probabilistic - each outcoming activity has some probability of appearance.

GERT vs. other network diagrams It's much less popular than PERT (Program Evaluation and Review Technique) or CPM (Critical Path Method) however, it allows some of those methods limitations to be addressed. The main limitations of PERT or CPM that might be addressed by GERT are:

there are no alternative paths - all activities have to be performed there are no loops - it is not possible to repeat activity, next similar activity has to be added there are no decisions in the diagram - no and, or, xor options which help to choose proper path there is no scaling - it is not possible to replace some detailed group of activities with the one summary task. GERT can help address these but at the cost of more sophisticated diagrams.

References

Worked examples

Example 1 — a first encounter with Graphical Evaluation and Review Technique

Start with the simplest possible case. Write down what Graphical Evaluation and Review Technique 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 Graphical Evaluation and Review Technique 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 Graphical Evaluation and Review Technique 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 Graphical Evaluation and Review Technique

In research: Graphical Evaluation and Review Technique 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 Graphical Evaluation and Review Technique 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: Graphical Evaluation and Review Technique is common in secondary-school and first-year university syllabi. It links to neighbouring topics Business stubs, Network analysis, Project management techniques, so understanding it makes those chapters shorter.
In everyday life: Look for Graphical Evaluation and Review Technique 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 Graphical Evaluation and Review Technique in 20 minutes

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

Frequently asked questions

What is Graphical Evaluation and Review Technique in simple terms?

Why does Graphical Evaluation and Review Technique 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 Graphical Evaluation and Review Technique?

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 Graphical Evaluation and Review Technique.