Learn About Controlled Variables

Biology Quiz - Unit 4 - Controlled Variable (Questions)

Good experiments change just one thing at a time. This GCSE Biology quiz explores controlled variables and why they make results more trustworthy.

Explore the Topic →

(quiz starts below)

Fascinating Fact:

In a plant growth experiment, factors such as light intensity, temperature and type of soil are often controlled variables. Only the chosen independent variable should be changed.

In GCSE Biology, you plan investigations by choosing one independent variable to change and then keeping all controlled variables the same. This makes your results fair, repeatable, and easier to trust when drawing conclusions.

Key Terms

Controlled variable: A factor that is kept the same in every test so it does not affect the results.
Independent variable: The factor you deliberately change to see its effect on the outcome.
Dependent variable: The factor you measure in an experiment, which may change because of the independent variable.

Frequently Asked Questions (click to see answers)

What is a controlled variable in GCSE Biology experiments?

A controlled variable is any factor that you keep constant during an experiment, such as temperature or light, so that only the independent variable affects the results.

Why are controlled variables important when planning an investigation?

Controlled variables are important because they reduce sources of error. If everything except the independent variable stays the same, you can link changes in the dependent variable more confidently to that one factor.

What are examples of controlled variables in a plant growth experiment?

In a plant growth experiment, controlled variables might include the same type of plant, the same volume of water, identical soil, and a constant temperature for all pots.

Try These Related Quizzes

Control variables are...

[ ]	all of the factors
[ ]	all the factors apart from the dependent and independent variables
[ ]	none of the factors
[ ]	the key independent variable

Unless we keep the controlled variables the same, the investigation will not be...

[ ]	correct
[ ]	fair
[ ]	right
[ ]	wrong

In an experiment on the effect of temperature on germination of cress seeds, which of the following would be controlled variables?

[ ]	Temperature and size of seeds
[ ]	Size of seeds and time
[ ]	pH and temperature
[ ]	Temperature and volume of water

What is a variable?

[ ]	Any factor involved in the experiment
[ ]	No factor of relevance
[ ]	Only the controlled variable
[ ]	The factor we change

If we fail to control variables, the results from the experiment may not be...

[ ]	real
[ ]	sufficient to draw a conclusion
[ ]	accurately recorded
[ ]	valid

A fair test is one where everything is the kept same except for the...

[ ]	dependent variable
[ ]	controlled variable
[ ]	independent variable
[ ]	any variable

During a drug trial, which of the following are controlled variables?

[ ]	Age and lifestyle
[ ]	Gender and age
[ ]	Gender and household income
[ ]	Age and household income

We control the controlled variables by keeping them...

[ ]	constant
[ ]	different
[ ]	larger
[ ]	smaller

In an experiment investigating the effect of acid concentration, which of these is a controlled variable?

[ ]	Volume
[ ]	Size of beaker
[ ]	Same beaker
[ ]	Time of day

10.

In an ecology experiment, we must always use quadrats of the same...

[ ]	material
[ ]	volume
[ ]	mass
[ ]	size

You can find more about this topic by visiting BBC Bitesize - Practical skills

Biology Quiz - Unit 4 - Controlled Variable (Answers)

Control variables are...

[ ]	all of the factors
[x]	all the factors apart from the dependent and independent variables
[ ]	none of the factors
[ ]	the key independent variable

Control variables should be kept as constant as possible during your experiment

Unless we keep the controlled variables the same, the investigation will not be...

[ ]	correct
[x]	fair
[ ]	right
[ ]	wrong

A fair test is where the controlled variables are kept constant

In an experiment on the effect of temperature on germination of cress seeds, which of the following would be controlled variables?

[ ]	Temperature and size of seeds
[x]	Size of seeds and time
[ ]	pH and temperature
[ ]	Temperature and volume of water

Temperature is the independent variable in this experiment so it cannot be a controlled variable. Any answer to this question containing the word temperature must therefore be wrong

What is a variable?

[x]	Any factor involved in the experiment
[ ]	No factor of relevance
[ ]	Only the controlled variable
[ ]	The factor we change

At the start of an investigation, you should list as many variables as you can

If we fail to control variables, the results from the experiment may not be...

[ ]	real
[ ]	sufficient to draw a conclusion
[ ]	accurately recorded
[x]	valid

The results will certainly be real but answers 2 and 3 depend on the person carrying out the experiment and not on controlled variables

A fair test is one where everything is the kept same except for the...

[ ]	dependent variable
[ ]	controlled variable
[x]	independent variable
[ ]	any variable

Only the independent variable is changed although the dependent variable will also be changing. The controlled variables remain constant

During a drug trial, which of the following are controlled variables?

[ ]	Age and lifestyle
[x]	Gender and age
[ ]	Gender and household income
[ ]	Age and household income

Lifestyle could have an effect on the results but is very complex and includes many other variables. It is for that reason that it would not really be regarded as a variable but more as a group of variables

We control the controlled variables by keeping them...

[x]	constant
[ ]	different
[ ]	larger
[ ]	smaller

Controlled variables must be kept the same