Variables in an experiment

Temperature is measured as the effect of soil depth so it is the dependent variable. In exams identify the measured outcome.

The amount of salt is the factor that the student deliberately changes, so it is the independent variable. The boiling time is measured and may change with the amount of salt, so it is the dependent variable. Controlled variables are conditions kept the same, such as the initial quantity of water. Exam tip: identify the variable deliberately changed in an experiment as the independent variable.

The amount of water evaporated is the measured outcome of the experiment and may change when the container’s surface area is changed. Therefore, it is the dependent variable. Surface area is the independent variable, while factors such as the initial amount of water should be controlled. Exam tip: The result that is measured or observed is usually the dependent variable.

Keeping temperature the same in all groups isolates the effect of sound intensity. Temperature is a controlled variable here.

The direct answer is A: independent variable. The student measures wax melting time at different temperatures. Temperature is intentionally changed from one trial to another, so it is the independent variable. The melting time responds to that change and is therefore the dependent variable, not listed as the answer here. A controlled variable would be kept the same, such as the mass or type of wax, container, or starting conditions. A constant is simply something that does not change during the test; temperature does change. B is the measured effect, C means kept equal, and D means unchanged. Memory cue: the input changed by the investigator is independent; the output measured is dependent.

Melting time is the measured result so it is the dependent variable. In exams identify the measured effect.

The amount of wax is kept the same so it is a controlled variable. In exams identify the factor kept constant.

Paper thickness is changed by the experimenter so it is the independent variable. In exams choose the deliberately changed property.

The absorption time is measured so it is the dependent variable. In exams identify the time measured as the outcome.

Keeping the drop volume the same allows a fair test of paper thickness. In exams treat it as a controlled variable.

The stretched length is deliberately changed so it is the independent variable. In exams identify the changed quantity.

Force is measured as a result of changing length so it is the dependent variable. In exams choose the measured outcome.

The type of rubber band is kept the same so it is a controlled variable. In exams identify constant conditions.

The amount of salt is changed by the experimenter so it is the independent variable. In exams identify the changed amount.

Boiling point is measured as the effect of salt amount so it is the dependent variable. In exams identify the outcome variable.

Keeping the initial amount of water the same ensures that only salt amount is tested. In exams treat it as a controlled variable.

The release height is deliberately changed so it is the independent variable. In exams choose the changed factor.

Flight distance is the measured result so it is the dependent variable. In exams identify the distance measured as the effect.

The plane design is kept the same so it is a controlled variable. In exams keep other conditions constant for comparison.

The amount of water added is changed so it is the independent variable. In exams identify the experimenter's change.

The drained water is the measured result so it is the dependent variable. In exams identify the measured quantity.

Soil type can affect drainage so it should be kept the same. In exams treat it as a controlled variable.

The lamp distance is changed so it is the independent variable. In exams identify the changed spatial factor.

Shadow length is measured as the effect of distance so it is the dependent variable. In exams choose the measured effect.

The direct answer is A, a controlled variable. A controlled variable is a condition deliberately kept unchanged so that the effect of the independent variable can be judged fairly. In a shadow experiment, the object's height may affect shadow length. Therefore, if the investigation changes another factor, such as the light’s position, the object's height should remain the same. Option A is correct because height is being held constant. Option B, the independent variable, is the factor intentionally changed, such as distance from the lamp, not the fixed height. Option C, the dependent variable, is the measured response, such as shadow length. Option D, a conclusion, is the statement made after examining the results; it is not a variable. Thus the fixed height is a controlled variable. Exam cue: “same throughout” usually signals a controlled variable.