Independent and Dependent?

Question

What is an independent variable and what is a dependent variable in science?

Answer 1

The independent variable is the one being deliberately altered to see the effects on the dependent variable (which is "dependent" on the independent variable). It is also the one that isn't changed by messing with other variables. For example, if you had a glass of cold water, the longer you left it out, the closer to room temperature it would get. Time is the independent variable, while temperature of the water is dependent on time, since the more time that passes, the warmer it gets. There is a direct relationship. However, if that glass of water is still really cold, it doesn't mean that no time has passed since you poured it. That is why time, in this instance, is independent.

Answer 2

Very roughly, independent is cause and dependent is effect.

For example, if you follow the rate of a reaction by plotting the change in concentration against time, time is independent and concentration is dependent.

But if you make up a series of solutions of known concentrations, and measure how long it takes them to do something (e.g. change colour), then concentration is your independent variable and time is the dependent variable.

Hope this helps.

Answer 3

The independent variable is the one that either i) you manipulate (e.g. you  mix the same chemicals in water but heat one to 10C and the other to 50C - temperature would be the independent variable, as you are controlling it), or ii) the one that 'would exist anyway' (e.g. in social sciences someone's gender would be the independent variable).

The dependent variable is the one that changes based on what is happening to the independent variable (it depends on the state of the independent variable). so in the example in (i) above, the speed at which the reaction takes place would depend on the temperature that you heated the solution to, making the rate of the reaction the dependent variable.  In two above, perhaps the amount of make-up someone is wearing would depend on their gender (not in every case, but on average in many societies), so 'amount of make-up' would be the dependent variable.

If you try to reverse the examples, it helps to 'get it' - e.g. you would see that you didn't increase the speed of the reaction to change the temperature, and that people don't (physically) change genders based on how much make-up they put on in the morning.

I hope that helps.

Answer 4

Independent variable is the thing that you change in the experiment.  The dependent variable is what is measured at the end of the experiment as a result of that change