Understanding and Designing Fair Tests in Scientific Investigations

• How will you test it fairly?
• What things should stay the
same?
Science helps us answer
questions using a fair test.

Learning Goals
At the end of the lesson, you will be able to:
✔ Define a fair test
✔ Identify features of a fair test
✔ Identify variables in an experiment
✔ Design a simple fair test

What is a Fair Test?
A fair test is a scientific investigation where:
• Only one factor is changed
• All other conditions stay the same
• Results are accurate and reliable
This helps us know the REAL cause of
change

What is an Investigation?
A scientific investigation is a way of
answering questions using evidence.
Scientists:
• ask questions
• test ideas
• collect data
• draw conclusions

Do we do “fair tests” in everyday life?
Examples:
• Comparing which ballpen writes
smoother
• Testing which online game is more fun
• Checking which online game loads faster
Science helps us find true and reliable

Why Do We Need Fair Tests?
Without a fair test:
• Results may be wrong
• We cannot trust the outcome
• We don’t know the real cause
With a fair test:
• Results are fair and correct
• We can trust the conclusion

Variables
Variables are factors that can change in an
experiment.
1.Independent variable – what you change
2.Dependent variable – what you measure
3.Controlled variables – what stays the same

• The factor that is changed on
purpose
• The cause in an experiment
Example:
• Type of cleaning solution used
Independent Variable

• The factor that is observed or
measured
• The effect of the experiment
Example:
• How clean the glass becomes
Dependent Variable

• Factors that must stay constant
• Make the test fair
Example:
• Same size glass
• Same amount of dirt
• Same cloth used
• Same pressure and time
Controlled Variables

1. Change one independent
variable at a time.
The independent variable is the factor, or
cause, that you change in an
experiment. Only one independent
variable must be changed at a time to
see how it affects the other factor in an
experiment.

2. Measure the dependent variable
accurately.
The dependent variable is the factor that
you observe or measure in an
experiment, or the effect. This shows
the result of changing the independent
variable

1. Keep the controlled variables
the same.
The controlled variables are the factors
kept constant throughout the
experiment. This is done to ensure that
the changes observed in the dependent
variable are only due to the independent
variable.

EXAMPLE
The teacher Ann wants to test which drink helps
students focus better during a short quiz: Milo or
juice. She gives one group of students the same
amount of Milo and another group the same
amount of juice. After drinking, both groups take
the same quiz at the same time, in the same
classroom, with the same time limit and
instructions. She then compares how focused the

Doing a fair test in a science investigation
is just like running in a race. The runners
(independent variable) run the same
distance, wear the same shoes, and start
at the same time (controlled variables),
but they will finish at different times
(dependent variable).

Mnemonic Device
helps you remember an idea or
information. It uses patterns of letters or
ideas to improve memory recall and
retention.
ROYGBIV

Assessment
• What is a fair test?
• What is the independent
variable?
• Give one controlled variable in
an experiment.
• Why do we need fair tests?

ACTIVITY BY COLUMN
Create a mnemonic for the features
of a fair test. Make sure that it is
creative and easy to understand.

ASSIGNMENT
• 4 plastic cups
• Marker
• 4 equal slices of banana
• Vinegar solution

ASSIGNMENT
• 4 plastic cups
• Marker
• 4 equal slices
of banana
• 1 teaspoon
vinegar
• Paper towels
• ½ teaspoon
salt
• Lemon
• Brush

Understanding and Designing Fair Tests in Scientific Investigations