Lesson Plan

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Lesson Plan
Grade: Date: 25/02/2026
Subject: Computer Science
Lesson Topic: Show understanding of lossy and lossless compression and justify the use of a method in a given situation
Learning Objective/s:
  • Describe the difference between lossy and lossless compression.
  • Explain how common algorithms (e.g., Huffman, JPEG) achieve compression.
  • Analyse a scenario and justify the most appropriate compression method based on data fidelity, storage/bandwidth and processing constraints.
  • Compare compression ratios and quality impacts of typical lossless and lossy techniques.
Materials Needed:
  • Projector or interactive whiteboard
  • Computer with internet access
  • Sample image and audio files for compression demos
  • Worksheet with comparison table and case‑study questions
  • Software: online Huffman visualiser, image editor (e.g., GIMP) for JPEG steps
  • Whiteboard and markers
 Introduction:
Begin with a quick poll: “When you download a photo, do you think any data is lost?” This activates prior knowledge of data storage. Explain that today’s success criteria are to differentiate lossy vs lossless methods and to justify a chosen method for a given use‑case.
Lesson Structure:
  1. Do‑now (5’) – Students list examples of files they have compressed and note whether they think the process was lossless or lossy.
  2. Mini‑lecture (10’) – Define compression, contrast lossy vs lossless, show a Huffman tree and JPEG workflow.
  3. Guided practice (12’) – In pairs, use an online Huffman tool to encode a short text and interpret the result.
  4. Demonstration (8’) – Walk through JPEG compression steps on a sample image, highlighting where data is discarded.
  5. Case‑study analysis (15’) – Groups evaluate three scenarios and select the best compression method, recording justification.
  6. Whole‑class debrief (5’) – Groups share decisions; teacher highlights key justification factors.
  7. Exit ticket (5’) – Students write one situation where lossless is essential and one where lossy is acceptable.
Conclusion:
Review that lossless methods preserve exact data while lossy methods trade fidelity for higher ratios. Remind students that choosing a technique depends on purpose, constraints, and acceptable quality loss. For homework, ask them to find a real‑world compression algorithm not covered and explain why it fits its application.