Variables and fair comparisons
The idea
An independent variable is deliberately changed; a dependent variable is measured. Controlled conditions are kept as consistent as practical. A fair comparison reduces competing explanations, but it does not eliminate every source of uncertainty. Define how each measurement will be made.
Worked example
To study light and plant growth, vary light exposure and measure height. Keep plant type, starting age, soil, and watering comparable. Several plants per condition help reveal natural variation.
Another application
For a paper-airplane study, changing paper type and fold at the same time makes interpretation harder. Keep one consistent while studying the other, repeat flights, and describe the launch procedure.
A common misunderstanding
A comparison can be confounded when several conditions change together. If light and watering both differ, the result does not isolate the effect of light.
Try it yourself
Design a paper-airplane investigation changing one fold. Define flight distance, starting point, and launch method. Work indoors away from people’s faces.
Check your understanding
In a light-versus-growth study, which variable is measured?
Reveal the explained answer
Plant growth, such as change in height, is the dependent variable.