The Scientific Method and Variables

The one thing you deliberately change; usually appears as a list of chosen values (e.g. 10, 20, 30 °C).

The thing you measure, which you think depends on the IV; usually comes with a unit or measuring instrument.

Everything else kept the same so the experiment is a fair test.

I change it, D depends on it, C stays constant. Or: "I am changing ___ to see what happens to ___, while keeping ___ the same."

It must be testable and falsifiable, ideally in "If… then… because…" form (e.g. plants under 12 h light will be taller after 3 weeks than plants under 4 h).

A controlled variable is a factor kept the same; a control group is an extra set-up with no treatment (or IV at zero) that gives a baseline for comparison.

A second factor that changes alongside the IV, so you cannot tell which one caused the result — the conclusion is not valid.

An experiment in which only the independent variable changes; all other variables are controlled.

A placebo is a fake treatment given to the control group; in a double-blind trial neither patient nor doctor knows who got the real drug, which removes bias.

Observation → question → hypothesis → experiment → data and analysis → conclusion → evaluation and repetition.

IV = drop height; DV = bounce height; CVs = same ball, same surface, same room temperature.

IV = temperature; DV = time taken for the starch to be digested.