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Year 10
OCR

Comparing compression algorithms

I can compare the suitability of different compression algorithms.

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New
New
Year 10
OCR

Comparing compression algorithms

I can compare the suitability of different compression algorithms.

Download all resources
Share activities with pupils

These resources will be removed by end of Summer Term 2025.

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Lesson details

Key learning points

  1. Different compression algorithms achieve the same goals in different ways.
  2. Compression methods can be compared based on file size reduction, (de)compression speed, and compressed data quality.
  3. The best compression method depends on the intended application, acceptable processing time and desired quality.

Keywords

  • Algorithm - a set of step-by-step instructions that are followed to perform a task

  • Efficiency - how effectively compression reduces the size of data while maintaining its usability

  • Trade-off - the limitations and choices faced when trying to optimise multiple competing factors

Common misconception

The best compression method is the one that makes files the smallest.

Smaller isn’t always better, sometimes important details are lost. The best method depends on the file type, quality needs, and purpose.


To help you plan your year 10 computer science lesson on: Comparing compression algorithms, download all teaching resources for free and adapt to suit your pupils' needs...

Encourage students to think about the type of data being compressed and what's important before choosing a compression method.
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Licence

This content is © Oak National Academy Limited (2025), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

Lesson video

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Prior knowledge starter quiz

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6 Questions

Q1.
What does encoding mean in data compression?
deleting redundant data
encrypting data
increasing file size
Correct answer: changing data into a different format
Q2.
What is used to visually represent the encoding scheme in Huffman coding?
Correct Answer: Huffman tree, tree, a tree
Q3.
What lossless compression technique reduces file size by encoding repeating sequences of data?
Correct Answer: run length encoding, RLE
Q4.
What term describes repeated or extra data that can be removed without losing essential meaning?
Correct Answer: redundancy, redundant data
Q5.
What is run length encoding?
Correct answer: a type of lossless compression
a type of lossy compression
a method to increase file size
a way to encrypt data
Q6.
What is the main goal of Huffman coding?
to delete redundant data
to increase file size
Correct answer: to assign shorter bit sequences to more frequent characters
to create repeating sequences

Assessment exit quiz

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6 Questions

Q1.
Match each term to its definition.
Correct Answer:algorithm,a set of step-by-step instructions to perform a task

a set of step-by-step instructions to perform a task

Correct Answer:efficiency,how effectively compression reduces file size while ensuring usability

how effectively compression reduces file size while ensuring usability

Correct Answer:trade-off,the limitations and choices faced when optimising competing factors

the limitations and choices faced when optimising competing factors

Correct Answer:compression speed,how quickly data can be compressed or decompressed

how quickly data can be compressed or decompressed

Q2.
Why is compression efficiency important?
Correct answer: It balances file size reduction with usability.
It deletes redundant data.
It encrypts files.
It increases file size.
Q3.
What does compression speed refer to?
how small the file becomes
how much data is deleted
how large the original file is
Correct answer: how quickly data can be compressed or decompressed
Q4.
Why isn’t the smallest file size always the best result for compression?
Smaller files take longer to compress.
Correct answer: Smaller files might lose important details.
Smaller files are harder to share.
Smaller files are less secure.
Q5.
What is a limitation of some compression methods?
They always make files larger.
They always delete important data.
Correct answer: They may reduce quality.
They cannot be used for images.
Q6.
Put these steps in order for comparing compression methods:
1 - Identify the file type.
2 - Determine the quality requirements.
3 - Compare the speeds of different methods and the resulting file sizes expected.
4 - Select the best method.