You will learn
- Define a fair test.
- Spot unfair tests.
- Control variables.
- Run a fair test with repeats.
Version 0.2 · expanded edition · built from cited public sources Content is based on the official frameworks and sources listed under Sources and standards. No official endorsement is claimed. Written in the style of common primary school assessments. No exam result is promised.
Student lesson
- In a fair test only one thing changes.
- All other variables are controlled.
- We repeat to be more sure.
- Unfair tests give unreliable results.
Words to know
a test where only one thing changes
to keep a variable the same
to do again
an unfair influence on a result
1. Discover: The paper towel test
Two groups test which paper towel absorbs the most water. Group A uses a big towel and a full cup. Group B uses a small towel and a half cup. “The results cannot be compared,” says the teacher. “Size and water amount were different.”
Think: What should they control?
2. Understand: Fair tests
Idea 1: What makes a test fair?
In a fair test only one thing changes. Everything else is controlled: kept the same. Then any difference in results is due to the thing we changed.
Idea 2: Spotting unfair tests
If two things change at once, we cannot tell which one caused the result. This is bias. We fix it by controlling the extra variable.
Idea 3: Repeating
Repeat the test at least three times. If results are close, we trust them more. Use the middle or average value.
3. Worked examples
Example 1 (I show you): Unfair?
Different sizes of towel.
- Size changed too.
- Cannot compare.
- Unfair.
Answer: Two things changed, so it is unfair.
Example 2 (We do it together): Control
Use same size and water.
- Same size.
- Same amount.
- Fair.
Answer: Control the extra variables.
Example 3 (You try): Repeat
Three tries.
Show the steps and answer
- 10, 11, 10 ml.
- Close.
- Trust it.
Answer: Close repeats give confidence.
Did you know?
Medical trials use fair tests with thousands of people to be sure a medicine works.
Why this matters
Fair tests give trustworthy evidence.
4. Explore: Absorbency fair test
Compare three paper towels fairly.
- Cut equal squares.
- Use the same water amount.
- Count drops absorbed.
- Repeat three times.
Think about it: what did you notice?
What did you notice? The fair test gave a clear winner.
5. Practise
Say it in a sentence
Use these starters when you talk about the lesson. Say them out loud.
- A fair test changes only ___ thing.
- We ___ the other variables.
- We ___ the test.
- Bias makes tests ___.
Guided practice
Question 1. What is a fair test?
Only one thing changes.
Question 2. What does control mean?
Keep the same.
Question 3. Why repeat?
Be more sure.
Independent practice
Level 1: Start
- What is a fair test?
- What does control mean?
- Why repeat?
- What is bias?
- How many repeats?
Level 2: Grow
- Why not change two things?
- What should stay the same in a towel test?
- How do we find a middle value?
Level 3: Stretch
- Spot an unfair test.
- Run a fair test.
- Average three results.
Answers are in the answer key below. Try first, then check.
6. Apply: Science in everyday life
Where have you seen unfair tests?
Show a sample answer
Races with different starts.
Another one. Tell a family member one thing from this lesson. Use the words you learned.
Show a sample answer
A clear sentence that uses at least one word from Words to know.
7. Common mistakes
Fix: Change one.
Fix: Repeat.
8. Lesson summary and revision card
- I can define a fair test.
- I can spot unfair tests.
- I can control variables.
- I can run a fair test with repeats.
9. Check and master
Answer all 14 questions. You will see feedback after each one.
Your result appears here after you answer every question.
10. Key takeaways
- In a fair test only one thing changes.
- All other variables are controlled.
- We repeat to be more sure.
- Unfair tests give unreliable results.
11. Next lesson
Next lesson: Recording results. Keep going with the next idea in this course.
Exam practice
These questions are written in the style of common school and international primary assessments. Try them on your own, without looking back. Then check your answers in the marking guide. The marks are shown in brackets.
- What is a fair test? [2 marks]
- Spot the unfair part in a test. [2 marks]
- Why repeat? [2 marks]
- Average 10, 12, 11. [2 marks]
- Safety rule? [2 marks]
Total: 10 marks.
Marking guide and model answers
- Change one thing [1]; control the rest [1]
- Two changes [1]; fix [1]
- More sure [1]; check [1]
- Sum 33 [1]; ÷3 = 11 [1]
- Small amounts [1]; wipe spills [1]
Score guide: 9 to 10 = secure. 6 to 8 = nearly there, revise the parts you missed. Under 6 = work through the lesson again with a grown-up.
Printable worksheet
- What is a fair test?
- What does control mean?
- Why repeat?
- What is bias?
- How many repeats?
- Why not change two things?
- What should stay the same in a towel test?
- How do we find a middle value?
- Spot an unfair test.
- Run a fair test.
Homework
Do a fair test at home with two kinds of paper towel. Record three repeats.
Answer key and marking scheme
| Question | Expected response | Marks |
|---|---|---|
| 1. What is a fair test? | Only one thing changes. | 1 |
| 2. What does control mean? | Keep the same. | 1 |
| 3. Why repeat? | Be more sure. | 1 |
| 4. What is bias? | An unfair influence. | 1 |
| 5. How many repeats? | At least three. | 1 |
| 6. Why not change two things? | Cannot tell the cause. | 1 |
| 7. What should stay the same in a towel test? | Size and water. | 1 |
| 8. How do we find a middle value? | Average. | 1 |
| 9. Spot an unfair test. | Explain. | 1 |
| 10. Run a fair test. | Table. | 1 |
| Total | 10 |
Independent practice answers. Level 1: 1 Only one thing changes.; 2 Keep the same.; 3 Be more sure.; 4 An unfair influence.; 5 At least three.. Level 2: 1 Cannot tell the cause.; 2 Size and water.; 3 Average.. Level 3: 1 Explain.; 2 Table.; 3 Calculation..
Quiz answers: 1 B, 2 C, 3 A, 4 B, 5 C, 6 A, 7 B, 8 C, 9 A, 10 B, 11 C, 12 A, Challenge 1 B, Challenge 2 C.
Mastery and remediation
| Objective | Bronze (Developing) | Silver (Proficient) | Gold (Advanced) |
|---|---|---|---|
| O1 Define a fair test | Shows this with help from an adult or a picture | Does this independently and explains how they know | Explains it clearly and uses it in a new situation |
| O2 Spot unfair tests | Shows this with help from an adult or a picture | Does this independently and explains how they know | Explains it clearly and uses it in a new situation |
| O3 Control variables | Shows this with help from an adult or a picture | Does this independently and explains how they know | Explains it clearly and uses it in a new situation |
| O4 Run a fair test with repeats | Shows this with help from an adult or a picture | Does this independently and explains how they know | Explains it clearly and uses it in a new situation |
Courseversity badge thresholds (overall quiz score): Gold = 90–100%; Silver = 80–89.9%; Bronze = 70–79.9%. A badge is never a full record of progress.
If a learner struggles
- Find the misconception: “Change everything to be sure.” Change one.
- Explain another way: use real objects, pictures or actions first, then words.
- Show a simpler example: Run and explain a fair test with repeats.
- Guided practice: work through one example together and let the learner try the next one.
- Reassess: use the quiz again or the worksheet.
- Move on when the learner shows Silver-level evidence independently.
For parents and guardians
In this lesson your child learns what makes a test fair. You do not need to be an expert to help.
- Make a race fair together.
- Ask, “What is the same?”
- Repeat a test.
- Ask “how do you know?” after each answer, and listen.
- Praise effort, not only right answers. Mistakes are how we learn.
- Ten to fifteen minutes a day is better than one long session.
Teacher package
1–5. Objectives, prerequisites, materials, preparation, duration
Lesson objectives. Learners will: define a fair test; spot unfair tests; control variables; run a fair test with repeats.
Prerequisite knowledge. Grade 2 science ideas: observing carefully, making predictions, measuring with simple tools and running simple fair tests.
Materials. Paper towels, cups, droppers, rulers and tables. Low-resource options: use chalk or charcoal on a board or wall, drawings in the sand, and objects from the classroom instead of printed materials.
Preparation. Cut equal squares. Prepare cups and droppers.
Suggested duration. 45–60 minutes. It can be split into two shorter sessions.
6–9. Teaching procedure, explanation notes, guided and independent activities
Introduction (5 min). Show two uneven tests and ask, “Which is fair?”
Explanation (10 min). Teach fair tests.
Guided activity (10 min). Learners run fair tests.
Independent activity (10 min). Learners compare.
Assessment and reflection (5 min). Ask each learner to say one thing they learned and how they know it.
Key questions. What changed? What stayed the same?
Teacher explanation notes. Start with real objects and safe, hands-on observation. Then talk about what was seen, then draw and write. Always say “how do you know?”. Keep to the safety notes, and use local, safe materials.
10–12. Differentiation, formative assessment, common misconceptions
Support. Use real objects and pictures, short sentences and a partner. Let learners point, show or draw instead of writing. Extension. Ask learners to find a new example at home and explain how they know.
Formative assessment. Listen to learners read and explain, ask “how do you know?”, and check the independent work.
Misconceptions. “Change everything to be sure.” Change one.
13–15. Assessment questions, answer keys, marking scheme
Use the quiz, the 10-mark exam practice and the worksheet on this page. All answers and marking guides are in the answer sections above. Re-check every answer before use.
16–19. Remediation, enrichment, homework, teacher reflection
Remediation. Run and explain a fair test with repeats. Enrichment. Look for one new example near your home or school, draw it and explain it to someone. Homework. See above.
Teacher reflection. After teaching, record: which ideas learners understood; which misconceptions occurred; which activities worked; which learners need more practice; and what to improve next time.
Sources and standards
This lesson is based on the sources below, and no official endorsement is claimed. Reference starting points: Next Generation Science Standards, Cambridge Primary Science and the IB Primary Years Programme. Where a standard code is named, it points to the official framework.
Research used to shape this lesson. Courseversity Science curriculum, Grade 3 Unit 1, topic 6; Next Generation Science Standards, science and engineering practices (asking questions, planning and carrying out investigations, analysing data); Cambridge Primary Science Stage 3, thinking and working scientifically; IB Primary Years Programme, how the world works. These sources informed the lesson.