The amount of water given to seeds is changed and seedling length is measured. Which is the independent variable?

Correct answer: Amount of water

The answer is A, amount of water. The independent variable is the factor deliberately changed by the investigator. Here, different amounts of water are given to the seeds, so water amount is the independent variable. The measured response is seedling length, making B the dependent variable, not the independent one. C, type of seed, should normally be kept the same so that seed type does not confuse the comparison; it is a controlled variable. D, amount of soil, should also be kept constant for a fair test and is another possible controlled variable. Thus the reasoning is: changed = water amount, measured = seedling length, kept same = seed type and soil amount. Memory cue: the independent variable is the experimenter’s chosen input; the dependent variable is the plant’s measured output.