1. Independent Variable (IV)
What it is:
The factor you purposely change in an experiment.
Why it’s important:
Helps you test your question: “What happens if…?”
Shows the cause in a cause-and-effect relationship.
Examples:
Changing the temperature of water
Changing the amount of fertilizer
Changing the type of food an animal eats
Changing the type of surface a ball rolls on
Extra Notes:
You must only change ONE independent variable at a time.
If you change more, you won’t know which one caused the result.
2. Dependent Variable (DV)
What it is:
The factor you measure or observe.
Why it’s important:
Shows the effect of the independent variable.
Examples:
Height of a plant
Speed of an animal
Temperature change
Number of bacteria growing
Extra Notes:
The dependent variable depends on the independent variable.
It is always something that gives data (numbers or observations).
3. Controlled Variables (Constants)
What they are:
The factors you keep the same throughout the experiment.
Why they’re important:
To make the experiment fair
To make the results trustworthy
To make sure only the independent variable affects the outcome
Examples:
If testing plant growth:
Same pot
Same soil
Same type of plant
Same amount of water
Same temperature
Same location
Extra Notes:
If you don’t control variables, your result becomes wrong or unreliable.
Controlled variables are sometimes called “fixed variables.”
⭐ Other Types of Variables (Extra Knowledge)
(Schools rarely teach these — bonus information!)
4. Extraneous Variables
Variables that you don’t want to affect the experiment but might.
Example: A sudden weather change during a plant experiment.
5. Confounding Variables
Variables that actually change the result but you didn’t control them.
Example: One plant gets more sunlight accidentally.
6. Categoric Variables
Variables described in words (not numbers).
Example: Types of shoes, types of animals.
7. Continuous Variables
Variables measured in numbers (height, temperature, speed).
8. Responding Variable
Another name for dependent variable.
⭐ Common Mistakes Students Make
Changing more than one independent variable.
Forgetting to control variables.
Measuring the wrong dependent variable.
Writing the independent variable in the form of a question.
Mixing up “what you change” and “what you measure.”