The Scientific Method and Variables
Key terms and skills for identifying variables and evaluating experiments.
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Questions Covered in This Set
12 cards to master
Independent variable (IV)
The one thing you deliberately change; usually appears as a list of chosen values (e.g. 10, 20, 30 °C).
Dependent variable (DV)
The thing you measure, which you think depends on the IV; usually comes with a unit or measuring instrument.
Controlled variables (CVs)
Everything else kept the same so the experiment is a fair test.
Memory hook for the three variables
I change it, D depends on it, C stays constant. Or: "I am changing ___ to see what happens to ___, while keeping ___ the same."
What makes a good hypothesis?
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).
Difference between a controlled variable and a control group
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.
Confounding variable
A second factor that changes alongside the IV, so you cannot tell which one caused the result — the conclusion is not valid.
Fair test
An experiment in which only the independent variable changes; all other variables are controlled.
Placebo and double-blind trial
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.
Steps of the scientific method
Observation → question → hypothesis → experiment → data and analysis → conclusion → evaluation and repetition.
Ball-drop experiment: name the IV, DV and CVs
IV = drop height; DV = bounce height; CVs = same ball, same surface, same room temperature.
Amylase and starch at 10–50 °C: name the IV and DV
IV = temperature; DV = time taken for the starch to be digested.
