Data quality: bias

Name:

Date:

Class:

Quick Questions

Shade in the A or B circle for each question.

1. A school surveys only students in the library at lunch about how much they enjoy studying. Is the data likely to be biased?

A No, because any students who answer make the data fair

B Yes, it is biased because it only samples students who choose to be in the library

2. Which survey question is a leading question that creates biased data?

A "Don't you agree that our amazing canteen has great food?"

B "How would you rate the canteen food from 1 to 5?"

3. Biased data unfairly favours one view or group because of how it was collected or selected.

A True

B False

4. A company surveys customers about a new app, but only by emailing people who already use the app. What is the main problem?

A The data is too quantitative to be useful

B Missing groups: people who stopped using or never tried the app are left out

5. Which sample is LESS likely to give biased data about the music tastes of all Year 10 students?

A Randomly selecting students from every Year 10 class

B Asking only the members of the school band

Match the Pairs

Draw a line connecting each item on the left to its match on the right.

Left column		Right column
1Sampling bias		APoll about school canteen food only given to the canteen's regular customers
2Leading question		BSurvey run online only, so students without internet at home are left out
3Missing groups in the data make the results unfair because some people's views are never recorded.		CThis is a leading question. The wording pushes respondents to agree, so the data is biased. It should be neutral, such as: "How would you rate the new timetable?"
4Biased data unfairly favours one view or group because of how it was collected or selected.		DOther year levels are missing from the sample, so it is biased. It should include a mix of students from every year level.
5Q: "Don't you agree the new timetable is terrible?"		EThe data comes from a sample that does not fairly represent the whole group, such as surveying only people at a gym about fitness habits.
6Sample: 50 Year 12 students asked about the whole school's study habits		FA survey question worded to push people towards a particular answer, which makes the responses unfairly favour one view.

Definitions

biased data

Fill in the Blanks

Complete each line of code by filling in the missing parts.

Data that favours one group is ______

=COUNTIF(C2:C99,"Yr 12")/______(C2:C99)

Q: "Don't you agree pizza is the best?" Problem: _______ question

Surveying only your friends is ________ bias

IF Year12Count = 0 THEN Biased = ____

Spot the Error

Shade in the letter of the line that contains an error.

Question 1

A population ← 800 students

B sample ← 40 chosen at random

C bias risk ← HIGH

Question 2

A survey ← app feedback

B Q1 ← Rate the app (1-5)

C Q2 ← How often do you use it?

D Q3 ← Why is it so easy to use?

Question 3

A goal ← views of all Year 11s

B groups ← Class 11A only

C ask ← each group

Question 4

A topic ← school start times

B population ← all students

C sample ← my friends only

D bias risk ← low

Question 5

A target ← all local residents

B contact ← landline phone only

C record ← every response

Answer Key

Data quality: bias

Section A: Quick Questions

B — Yes, it is biased because it only samples students who choose to be in the library

A — "Don't you agree that our amazing canteen has great food?"

A — True

B — Missing groups: people who stopped using or never tried the app are left out

A — Randomly selecting students from every Year 10 class

Section B: Match the Pairs

Sampling bias → The data comes from a sample that does not fairly represent the whole group, such as surveying only people at a gym about fitness habits.

Leading question → A survey question worded to push people towards a particular answer, which makes the responses unfairly favour one view.

Missing groups in the data make the results unfair because some people's views are never recorded. → Survey run online only, so students without internet at home are left out

Biased data unfairly favours one view or group because of how it was collected or selected. → Poll about school canteen food only given to the canteen's regular customers

Q: "Don't you agree the new timetable is terrible?" → This is a leading question. The wording pushes respondents to agree, so the data is biased. It should be neutral, such as: "How would you rate the new timetable?"

Sample: 50 Year 12 students asked about the whole school's study habits → Other year levels are missing from the sample, so it is biased. It should include a mix of students from every year level.

Section C: Definitions

biased data — Data that unfairly favours one view or group because of how it was collected or selected, e.g. sampling bias, leading questions or missing groups.

Section D: Fill in the Blanks

Data that favours one group is biased

=COUNTIF(C2:C99,"Yr 12")/COUNTA(C2:C99)

Q: "Don't you agree pizza is the best?"
Problem: leading question

Surveying only your friends is sampling bias

IF Year12Count = 0 THEN Biased = true

Section E: Spot the Error

C — A random sample gives every student an equal chance of being picked, so the risk of sampling bias is low. It should be: bias risk ← LOW

D — This is a leading question because it assumes the app is easy and pushes the answer. A neutral version is: Q3 ← How easy is it to use?

B — Only surveying one class leaves the other Year 11 classes out, so groups are missing from the data. It should include all classes: groups ← all classes

C — Choosing only friends is a convenience sample that does not represent the whole population, which causes sampling bias. It should be a random pick from the roll.

B — Landline-only contact misses people who only use mobiles or the internet, so those groups are missing from the data. Use more than one method: phone and online.