Variables in an experiment

Correct answer: C. Dependent variable

Bulb brightness is measured as the result of changing battery number. In exams choose the outcome variable.

Correct answer: D. Controlled variable

Keeping the bulb type the same ensures that only battery number is tested. In exams treat it as a controlled variable.

Correct answer: A. Changing water amount and measuring plant height with water amount as the independent variable

Water amount is changed by the experimenter so it is the independent variable. In exams identify the changed factor as the cause.

Correct answer: B. Measuring ice melting time at different temperatures

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

Correct answer: A. नई खाद के पौधों की वृद्धि पर प्रभाव जाँचते समय बिना खाद वाला समूह रखना

A control group is treated in the ordinary way and provides a baseline for comparison. When testing a new fertilizer, plants that receive no fertilizer show how much growth occurs without the treatment. The difference between treated and untreated groups can then be linked more confidently to the fertilizer. Options B and C concern procedure or observation, and D is not a valid experimental purpose.