# The difference between independent variables vs dependent variables?

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i’m trying to write a lab report and idk how to figure out which is which in the experiment

In: Biology

Independent is the variable or thing you change or swap in an experiment

Dependent variable is what is *affected* by the independent variable and subject to changes.

Example: Which Hot Wheel car will roll down my slope the fastest?

IV: Hot Wheel cars

DV: Time they finished

Will you be changing or manipulating the variable you want to identify?

The independent variable in a science experiment is the one the scientist changes. The dependent variable is the one the scientist wants to measure.

Let’s say you were growing potted vegetable plants — cucumbers, let’s say — and you wanted to know how much water they needed to grow best. You knew how much sun they needed, how often to water, all that, but not how *much* water to give the plant each time you watered.

So you get a single package of seeds from the store, split it between three pots, and put them somewhere in your house where they get the sunlight they need. You know the watering schedule too. You want to see the effects of water amounts A, B, and C.

To get your answer, you might use a marker to write on the pots how many milliliters of water to give each plant at a time. Then, each time you water your plants, you carefully measure out the three amounts of water you determined earlier. You do this for some set amount of time, say two months¹, and then you observe the growth.

Assuming you controlled for as much as you possibly could, the only thing *you* changed was the amount of water you gave each plant. Nature did the rest, and that will have shown as differing growth.

Independent variable (you changed): water amount.

Dependent variable (changed **depending** on what you did): differing plant growth.

Does that make sense?

¹ I have no idea how long cucumbers really need. Just pretend I do

The dependent variable DEPENDS on the independent one. The independent one varies on it’s own without influence from the dependent variable. Easy example. If our experiment was “how does rain impact corn crop growth?”, rain is the independent variable. The amount of rain that falls is independent of corn plant growth. But since corn plants require water, the corn growth is the dependent variable. It depends, in part, on the amount of rainfall.

Ultimately it is up to the scientist.

You could say “I want to study what time it is based on how bright the outdoors is”, or you could say “I want to study how bright it is outside based on what time it is”.

In the first example, brightness is the independent variable and time is the dependent, and vice versa.

Typically independent variables are what *you* change, and dependent variables are what you measure.

Let’s use this example: you want to see which fertilizer is best at increasing plant height.
Independent variable – this is what you are changing, in this case the fertilizer type.
Dependent variable – this *depends* on the changes you made to the independent variable, or in most cases it’s what you’re documenting and measuring. In this case it is plant height