Year 5 Science: Planning a fair test
Part of the Year 5 Science working scientifically: planning and reporting chapter. Chapter overview · whole chapter on one page
Planning a fair test
A scientific enquiry starts with a question, and a plan that can answer it. Scientists can plan different types of enquiry:
- a fair test, where only one thing is changed and everything else is kept the same;
- pattern seeking, where something is observed and measured over time, such as the number of birds in a garden each week;
- classifying, where things are sorted into groups using their features;
- research, where information is found in books or from reliable sources.
In a fair test there are three kinds of variable. A variable is a thing that can change.
- The independent variable is the one you change on purpose.
- The dependent variable is the one you measure. It depends on the change you make.
- Control variables are the things you keep the same.
Key ideas
- A fair test changes only one thing: the independent variable.
- The dependent variable is measured. It is the result of the test.
- Control variables are kept the same, so the test is fair.
- Other types of enquiry include pattern seeking, classifying and research.
Method. Read the labels in the diagram.
- Find the label for the same things. The labels say the car, surface and release point are kept the same.Kept the same: car, surface
- Choose the one that is kept the same. The surface is kept the same. The ramp height is the thing that is changed.the surface
- Write the answer. the surface
Check. Only the ramp height is changed on purpose. ✓
Watch out. The changed variable is never a control variable.
Method. Find the variable that is measured.
- Find the change on purpose. Mo changes the mass of the car on purpose, so mass is the independent variable.mass
- Find the measurement. Mo measures how long the car takes to roll, so time taken is the dependent variable.time taken
- Write the answer. time taken
Check. The time depends on the mass Mo chose. ✓
Method. Think about what else could change the time.
- Think about the test. The ramp, the surface and the release point could all change the time.ramp, surface, release
- Choose one to keep the same. Any one of these must stay the same for the test to be fair.Accept any one
- Write the answer. Accept any one of: the ramp height, the surface, the release point.
Check. Keep the control variables the same. ✓
Watch out
Watch out: a variable that you keep the same is a control variable. It is not the dependent variable, because you do not measure it.
Try it (with your teacher or a grown-up). Put a book under one end of a ramp (a board or a tray will do). Roll a toy car from the same starting point, three times with one book, and three times with two books. Keep the car, the surface and the starting point the same. Which variable did you change on purpose?
Exam tip
Grown-up tip. Ask: “What did you change on purpose? What did you measure? What did you keep the same?” Your child should answer with the words independent, dependent and control.
Exercise 1A Planning a fair test
Method. Find the variable that is changed on purpose.
- Read the test. Ruby changes the height of the ramp on purpose.height of the ramp
- Name the variable. The variable that is changed on purpose is the independent variable.the height of the ramp
- Write the answer. the height of the ramp
Check. The height of the ramp is the one thing that changes. ✓
Method. Find the thing that is measured.
- Read the test. Ruby measures how far the car rolls.how far the car rolls
- Name the variable. That is the dependent variable: the distance rolled.distance rolled
- Write the answer. distance rolled
Check. The distance depends on the ramp height. ✓
Method. Read the definition.
- Read the definition. The variable you change on purpose is called the independent variable.independent
- Fill the gap. So the missing word is independent.independent
- Write the answer. independent
Check. Independent means you are free to choose it. ✓
Method. Read the definition.
- Read the definition. The variable you measure depends on the change you make, so it is the dependent variable.dependent
- Fill the gap. So the missing word is dependent.dependent
- Write the answer. dependent
Check. It depends on the independent variable. ✓
Method. Think about what must stay the same.
- Think about the test. The car, the surface and the release point must stay the same.same car
- Write one. Any one of these is a correct control variable.one control variable
- Write the answer. Accept any one of: the same car, the same surface, the same release point.
Check. Keeping the control variables the same makes the test fair. ✓
Method. Think about how many things are changed.
- Count the changes. Tom changes three things at once: the car, the ramp and the surface.three things
- Decide. A fair test changes only one thing, so this is not a fair test.no
- Write the answer. no
Check. If three things change, you cannot tell which one made the difference. ✓
Method. Think about what Priya does over time.
- Read what she does. Priya observes and counts the birds each day, to see how the number changes over time.over time
- Name the type of enquiry. Observing and measuring something over time is pattern seeking.pattern seeking
- Write the answer. pattern seeking
Check. Pattern seeking looks for changes over time, not a test with one change. ✓
Method. Count the things that are changed.
- Read the test. Mo changes only the height of the ramp.only the height
- Count. Only one variable is changed on purpose, so the number is 1.1
- Write the answer. 1
Check. Three heights are tested, but the thing changed is always the same kind of variable: height. ✓
Method. Find the variable that Aisha changes on purpose.
- Read the test. Aisha changes the number of paper clips on purpose.number of paper clips
- Name it. The variable changed on purpose is the independent variable.number of paper clips
- Write the answer. number of paper clips
Check. The paper clips are added on purpose, so they are the independent variable. ✓
Method. Find what is measured.
- Read the test. Aisha measures how far the paper plane flies.how far it flies
- Name it. The thing measured is the dependent variable: the distance flown.distance flown
- Write the answer. distance flown
Check. The distance depends on the number of paper clips. ✓
Method. Think about what is kept the same.
- Think about the throw. Aisha keeps the throw the same, so it is not changed.kept the same
- Decide. A variable that is kept the same is a control variable, so the answer is yes.yes
- Write the answer. yes
Check. The throw is kept the same, so it is one of the control variables. ✓
Method. Think about the fair test.
- Think about the change. Only the ramp height should change on purpose.only the height
- Write the reason. If the release point changed, the distance could change for that reason too.could change
- Write the answer. Accept any sentence that says the release point must stay the same, so that only the ramp height changes and the test is fair.
Check. Keeping the release point the same keeps the test fair. ✓