Computer Science · Grade 9

Active learning ideas

Introduction to Data Analysis

Active learning works for this topic because compression and storage are abstract concepts that become tangible when students manipulate real data. Hands-on activities help students move from memorizing definitions to experiencing why lossless and lossy compression matter in everyday technology use.

• Ontario Curriculum Expectations
• CS.HS.DA.4
• CS.HS.S.2

• 25–35 min
• Small Groups
• 3 activities

Activity 01

• Inquiry Circle
• 30 min · Small Groups

Inquiry Circle: The Emoji Code

Groups are given a paragraph of text and must 'compress' it by replacing common words with symbols or emojis. They then trade their 'compressed' text and their 'key' with another group to see if it can be perfectly reconstructed.

Explain the purpose of data analysis in decision-making.

Facilitation Tip

During The Emoji Code, circulate to ask guiding questions like 'Why did you choose this symbol to represent that word?' to push students toward explaining their encoding choices.

What to look for

Provide students with a small table of data (e.g., student scores on a quiz). Ask them to: 1. Calculate the mean score. 2. Identify one trend or pattern they observe in the data. 3. State whether the data is primarily quantitative or qualitative.

• Analyze
• Evaluate
• Create
• Self-Management
• Self-Awareness

Activity 02

• Formal Debate
• 25 min · Small Groups

Formal Debate: Quality vs. Size

Students compare a high-resolution image with a highly compressed version. They engage in a debate about which version is better for different scenarios, such as printing a poster versus sending a quick text message in a remote area with slow internet.

Analyze simple datasets to identify key observations.

Facilitation Tip

For the Quality vs. Size debate, assign roles clearly so students prepare arguments based on the evidence they’ve gathered in previous activities.

What to look for

Pose the question: 'Imagine you are analyzing customer feedback for a new video game. What types of questions would you ask to gather quantitative data, and what types of questions would yield qualitative data? How might analyzing both types of data help the game developers?'

• Analyze
• Evaluate
• Create
• Self-Management
• Decision-Making

Activity 03

• Stations Rotation
• 35 min · Small Groups

Stations Rotation: File Format Safari

Set up stations with different file types (.zip, .jpg, .png, .mp3, .wav). Students record the file sizes of the same piece of media in different formats and hypothesize why some are much smaller than others.

Differentiate between qualitative and quantitative data analysis approaches.

Facilitation Tip

In the File Format Safari, provide a checklist with specific file types and their common uses to focus student observations.

What to look for

Present students with a scenario, such as a city council wanting to understand traffic patterns. Ask them to identify: 1. What is the primary goal of the data analysis? 2. What kind of data (quantitative or qualitative) might be useful? 3. What is one specific piece of information they hope to gain from the analysis?

• Remember
• Understand
• Apply
• Analyze
• Self-Management
• Relationship Skills

A few notes on teaching this unit

Experienced teachers approach this topic by starting with concrete examples students already use, like photos or music files, before introducing technical terms. Avoid jumping straight to algorithms or formulas; instead, let students discover the need for compression through frustration with large file sizes. Research shows that when students physically compress files or messages themselves, they grasp the concept faster than with lectures alone.

Successful learning looks like students explaining the trade-offs between file size and quality in their own words, using examples from the activities. They should also justify their choices in debates or station work with evidence from their investigations.

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Watch Out for These Misconceptions

• During The Emoji Code, watch for students who believe lossy compression always ruins the original data.

  After the activity, have students listen to the same song compressed at different quality levels and vote on which one they can still recognize; this demonstrates that some loss is acceptable in practice.

• During File Format Safari, watch for students who think compressing a file multiple times will keep reducing its size indefinitely.

  Provide students with a file that’s already been compressed and ask them to compress it again; they’ll see the size barely changes, illustrating the limit of redundancy removal.

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Methods used in this brief

• Inquiry Circle
• Formal Debate
• Stations Rotation