← VCE Data Analysis

Data quality: relevance

Data that relates directly to the question or purpose it is used for. Unneeded fields or data from the wrong population are not relevant, so they lower the quality of the information.

Part of: VCE Applied Computing - U1O1 - Data analysis — Module 31, VCE Data Analytics - U3O2 - Analysis and Design — Module 77, VCE Data Analytics - U4O2 - Cyber Security: Data Security — Module 24, ACARA Digital Technologies Years 9–10 — Acquiring and Validating Data — Module 85

Understanding Data quality: relevance in VCE Data Analysis

What it does: The question is about Year 11 students, but the data comes from Year 7 students, so it does not relate directly to the purpose. Only the fields needed to answer the question are kept, so the information is relevant and focused. Irrelevant data makes information less useful, so it lowers the quality of the information. Hair colour has nothing to do with library loans, so it is an unneeded field. LoanDate is relevant to when books are borrowed. This is the core definition of relevance as a data quality characteristic: the data fits the question being asked. Extra unneeded fields add clutter and lower the quality of the information because they do not relate to the purpose.

Common mistakes: The goal is the Year 10 maths average, so the field averaged must be MathsMark. ShoeSize is not relevant to the question. It should be SELECT AVG(MathsMark). The goal is about Year 10, but this line keeps Year 7 students. That is the wrong population, so the data is not relevant. It should be KEEP rows WHERE Year = 10.

Class: _____________________  ·  Name: _____________________  ·  Date: _________

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This module's key terms are also in a printable crossword (Modules 25–37) and word search (Modules 25–54).

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Learning
Duo
A school wants to know how many students use the canteen. Which data is relevant?
Canteen purchase records per studentStudents' favourite football teams
Matches
Purpose: Find the most popular canteen food. Data: students' bus routes and home postcodes
↓
The data does not relate to the purpose. Bus routes and postcodes are irrelevant. Collect canteen purchase or food preference data instead.
Applying
Meanings
Term
relevant data
Meaning
Data that relates directly to the question or purpose it is used for. Unneeded fields or data from the wrong population are not relevant, so they lower the quality of the information.
Practice
=COUNTIF(C2:C200,"Year 10")
Testing
Gaps
SELECT AVG(mark) FROM marks year = 10;
Check Answer
Spots
1SELECT AVG(ShoeSize)
2FROM Year10Results

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Quick Questions

1. A school wants to know how many students use the canteen. Which data is relevant?
A. Canteen purchase records per student ✓
B. Students' favourite football teams
Relevant data relates directly to the question being asked. Canteen purchases show canteen use, while football teams do not.
2. True or false: Relevance means the data relates directly to the question or purpose it is used for.
A. True ✓
B. False
Relevant data is data that directly helps answer the question or meet the purpose. Having a lot of data does not make it relevant.
3. A survey about bus use includes a field for each student's shoe size. What is the problem?
A. The shoe size field improves the relevance of the data
B. The shoe size field is an extra unneeded field that is not relevant ✓
Unneeded fields add clutter and lower the quality of the information because they do not help answer the question.
4. A council wants to know what local teenagers think of a new skate park. Which group should it survey?
A. Teenagers who live in the local area ✓
B. Adults living in another state
Data from the wrong population is not relevant. The council needs data from the group the question is about.
5. Which statement about relevance is correct?
A. Relevance has no effect on the quality of information
B. Relevance is a characteristic of information that affects its quality ✓
Irrelevant data makes information less useful, so it lowers the quality of the information.

Match the Pairs

relevant data → Data that relates directly to the question or purpose it is being used for
irrelevant field → A column of data that does not help answer the question, such as shoe size in a study of exam results
Data from the wrong population is not relevant to the question being asked → Question: Do Year 11 students sleep enough? Data: survey of Year 7 students
Relevance is a characteristic of information: only keep the fields that answer the question → Question: Average Year 10 maths mark? Keep: Student, Year, MathsMark
Purpose: Find the most popular canteen food. Data: students' bus routes and home postcodes → The data does not relate to the purpose. Bus routes and postcodes are irrelevant. Collect canteen purchase or food preference data instead.
Question: How many hours do VCE students study? Data: 500 responses from primary school students → The data is from the wrong population. Use responses from VCE students so the data is relevant to the question.

Key Term

relevant data
Data that relates directly to the question or purpose it is used for. Unneeded fields or data from the wrong population are not relevant, so they lower the quality of the information.

Fill in the Blanks

1. // Average score of Year 10 students SELECT AVG(mark) FROM marks WHERE year = 10;
Hint: Type the keyword that keeps only the rows from the right population.
2. // Show rainfall for each suburb SELECT suburb, rainfall FROM weather;
Hint: Type the field name that the purpose needs, so no unneeded fields are included.
3. =AVERAGEIF(B2:B30,"Year 10",C2:C30)
Hint: Type the spreadsheet function that averages only the rows matching a condition.
4. // Only keep adult respondents IF age >= 18 THEN KEEP record
Hint: Type the comparison operator that keeps ages 18 and over.
5. // Attendance for Year 7 students only SELECT * FROM students WHERE year = 7;
Hint: Type the year level that matches the population in the purpose.

Spot the Error

Question 1
A SELECT AVG(ShoeSize)
B FROM Year10Results
C -- Goal: Year 10 maths average
Line A — The goal is the Year 10 maths average, so the field averaged must be MathsMark. ShoeSize is not relevant to the question. It should be SELECT AVG(MathsMark).
Question 2
A GOAL: Year 10 maths average
B SET rows ← Students
C KEEP rows WHERE Year = 7
D SHOW average of MathsMark
Line C — The goal is about Year 10, but this line keeps Year 7 students. That is the wrong population, so the data is not relevant. It should be KEEP rows WHERE Year = 10.
Question 3
A GOAL: Students' lunch choices
B ASK ← parents of students
C QUESTION: Favourite lunch?
Line B — The goal is what students choose for lunch, so the survey must go to students. Asking parents gives data from the wrong population. It should be ASK ← enrolled students.
Question 4
A SELECT Name, Email, Weight
B FROM Students
C -- Goal: newsletter mailing list
Line A — A newsletter mailing list only needs names and email addresses. Weight is an extra, unneeded field that is not relevant to the purpose. It should be SELECT Name, Email.
Question 5
A GOAL: Geelong rain in 2023
B LOAD file: BoM_rain.csv
C FILTER Town = Geelong
D FILTER Year = 1998
Line D — The goal is rainfall in 2023, but this filter keeps 1998 data. Data from the wrong time period is not relevant. It should be FILTER Year = 2023.

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