Da VIP Academy / GED / Science / Scientific Practices & Data
Variables & Experimental Design
Identify independent, dependent, and controlled variables and spot design flaws.
How it works
Three kinds of variables
The independent variable is what the researcher changes. The dependent variable is what gets measured. Controlled variables are everything held the same so the comparison is fair.
One change at a time
If two things change at once, you cannot tell which caused the result. A good design also uses a control group and enough subjects to rule out chance.
Worked examples
In the bean-plant study, name the variables.
- Independent: hours of light per day.
- Dependent: average plant height.
- Controlled: soil, pot size, water amount, days grown.
Words to know
- Independent variable
- The factor the experimenter deliberately changes.
- Control group
- A group with no treatment, used for comparison.
Test-day tips
- • Ask 'what did they change?' then 'what did they measure?' — in that order.