← ACARA Digital Technologies Years 7–8

Generalising an exact value into a range

Replacing an exact value with a broader group, like a birth date with an age band, so the data is less identifying but still useful.

Part of: ACARA Digital Technologies Years 7–8 — Digital Footprints and Data Minimisation — Module 46, QCE Digital Solutions Unit 2 — Data and Programming Techniques — Module 123

Understanding Generalising an exact value into a range in ACARA Digital Technologies Years 7–8

What it does: The formula replaces an exact income with a band. The data is less identifying but can still show income groups. Using only the suburb column instead of the full street address is generalising, because a suburb covers many people, not one home. Ranges hide the exact detail that could point to one person, while keeping the pattern you need to analyse. A suburb or region is a broader group. A street number and name is still very identifying. Income bands group many people together, so no single person's exact income is shown. Band sizes should suit the question. One huge band hides the differences you want to compare.

Common mistakes: The program should share the age band, not the exact birth date. Outputting birthDate keeps the identifying value. It should be OUTPUT band. Generalising an address means sharing only the broader suburb. Sharing the street keeps the exact address. It should be shared ← suburb.

Class: _____________________  ·  Name: _____________________  ·  Date: _________

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This module's key terms are also in a printable crossword (Modules 752–770) and word search (Modules 696–770).

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Learning
Duo
A survey stores each student's exact birth date. Which change is an example of generalising?
Replace the birth date 14/03/2011 with the age band 12-13Replace the birth date 14/03/2011 with the student's name
Matches
=IF(B2<13,B2,"13 and over")
↓
The formula still returns the exact age for younger people, so it does not generalise those values. Both outcomes should be bands, such as "Under 13".
Applying
Meanings
Term
generalising
Meaning
Replacing an exact value with a broader group, like a birth date with an age band, so the data is less identifying but still useful.
Practice
SELECT firstName,
Testing
Gaps
=(B2<13,"Under 13","13 and over")
Check Answer
Spots
3band ← "13 to 15"
4OUTPUT birthDate

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Quick Questions

1. A survey stores each student's exact birth date. Which change is an example of generalising?
A. Replace the birth date 14/03/2011 with the age band 12-13 ✓
B. Replace the birth date 14/03/2011 with the student's name
Generalising swaps an exact value for a broader group. An age band is less identifying than a birth date but is still useful.
2. What is the main reason for generalising an exact value into a range?
A. It makes the data more exact so people can be found easily
B. It makes the data less identifying but still useful ✓
Ranges hide the exact detail that could point to one person, while keeping the pattern you need to analyse.
3. Which is a generalised version of the exact address '12 Wattle St, Brunswick'?
A. Brunswick ✓
B. 12 Wattle St
A suburb or region is a broader group. A street number and name is still very identifying.
4. A dataset lists exact incomes like $52,310. Which column is better for privacy?
A. Income: $52,310
B. Income band: $50,000-$59,999 ✓
Income bands group many people together, so no single person's exact income is shown.
5. You are studying which year levels use the school library. Which age grouping suits this question?
A. Bands that match year levels, like 12-13 and 14-15 ✓
B. One band for everyone, like 10-18
Band sizes should suit the question. One huge band hides the differences you want to compare.

Match the Pairs

=IF(B2<13,"Under 13","13 and over") → Turns an exact age into a broad age band so the exact number is no longer stored
=LEFT(C2,4) → Keeps only the first 4 characters of a value, such as a postcode, so it points to a wider area
Generalising an exact income into an income band so the exact amount is hidden → =IF(D2<50000,"Under 50k","50k or more")
Generalising a full street address into just the suburb → ="Suburb: "&B2
=IF(B2<13,B2,"13 and over") → The formula still returns the exact age for younger people, so it does not generalise those values. Both outcomes should be bands, such as "Under 13".
Age bands: 1 year, 1 year, 1 year → Bands that are only 1 year wide are almost as exact as the real age, so they still identify people. Use wider bands such as 10-12, 13-15 and 16-18.

Key Term

generalising
Replacing an exact value with a broader group, like a birth date with an age band, so the data is less identifying but still useful.

Fill in the Blanks

1. =IF(B2<13,"Under 13","13 and over")
Hint: Type the function that picks one label or another, turning an exact age into an age band.
2. =IF(B2<13,"Under 13","13 and over")
Hint: Type the comparison operator that tests whether the age is below the cut-off.
3. =LEFT(C2,2)
Hint: Type the function that keeps only the first characters of a postcode, giving a broad region instead of an exact one.
4. IF income < 50000 THEN band ← "Under 50k" ENDIF
Hint: Type the pseudocode keyword that starts the action when the income condition is true.
5. =IF(B2<13,"Child",IF(B2<18,"Teen","Adult"))
Hint: Type the function that adds a second test so the data has three age bands instead of two.

Spot the Error

Question 1
A birthDate ← "2011-05-14"
B age ← 14
C band ← "13 to 15"
D OUTPUT birthDate
Line D — The program should share the age band, not the exact birth date. Outputting birthDate keeps the identifying value. It should be OUTPUT band.
Question 2
A street ← "12 Oak St"
B suburb ← "Hawthorn"
C shared ← street
D OUTPUT shared
Line C — Generalising an address means sharing only the broader suburb. Sharing the street keeps the exact address. It should be shared ← suburb.
Question 3
A income ← 62000
B band ← "$62,000"
C OUTPUT band
Line B — An income band is a range, not the exact income. "$62,000" is still the exact value. It should be a range like "$50,000 to $79,999".
Question 4
A IF age < 16 THEN
B band ← "Under 16"
C ELSE
D band ← "Under 16"
Line D — Both groups were given the same label, so the data can no longer tell the groups apart. The ELSE branch should be band ← "16 and over".
Question 5
A ageBand ← 14
B rowID ← "P07"
C OUTPUT rowID, ageBand
Line A — The ageBand variable should hold a range such as "13 to 15". Storing 14 keeps the exact age, so nothing has been generalised.

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