Variables in Science: Independent, Dependent and Controlled!

This video explains independent, dependent, and controlled variables, with a special emphasis on controlling variables in experimental design. Helpful in understanding the scientific method!

What are variables? Is science, variables are all the things that can vary or change in an experiment.
To see how variables work, let’s set up an imaginary experiment testing the effect of vitamins on squid lifespan. Here are two groups of squid. One will receive vitamins and the other will not.
In this experiment (and every other experiment), there are 3 types of variables:
1. The Independent Variable: This is the variable that you manipulate, the thing that you are investigating. So, in an experiment testing how vitamins affect squid lifespan, the amount of vitamins given to your squid is the independent variable. As the experimenter, you decide to change this variable. It does NOT depend on any other variables in the experiment, which is why it is called the independent variable. Good experiments only have 1 independent variable!
2. The Dependent Variable: This is the variable that you are measuring. Think of this as your results. In our experiment, the dependent variable would be squid lifespan, because lifespan depends on what you changed in your experiment.
3. Controlled variables: These variables are all the things that you keep constant in your experiment. So, in our squid experiment, you would need to have many controlled variables. In fact, any variable that could affect your results (besides your independent variable) should be controlled. Temperature, food type, and water quality are all examples of controlled variables in this experiment and should be kept the same for both groups of squid.
Controlled variables are super important! If you fail to control your variables, your experimental results will be meaningless. Let’s see why.
Imagine that you don’t control these variables. The control group squid are kept in a tank with a temperature of 20oC and are given normal squid food and clean water (but no vitamins). But our experimental group is kept in a tank with a temperature of 90oC and fed nacho cheese while swimming in dirty water. We also give them vitamins.
Now, let’s say all our experimental group squid die after 2 hours. Does this mean that vitamins kill squid?
There is no way to know the effect of vitamins because we did not control our controlled variables! The squid could have died from being nearly boiled, or from nacho cheese, or from the dirty water! Because we did NOT control these variables, we CANNOT answer our question about the effect of vitamins on squid.
On the other hand, if we control our variables and make sure both groups get the same temperature, the same food, and the same water quality, and ONLY change the amount of vitamins (our INDEPENDENT VARIABLE), we will be able to answer our question.
So, remember! In an experiment, only change 1 variable (your independent variable), make sure you keep all other variables controlled, and then you will be able to measure your dependent variable or results.
Credits:
Music: www.bensound.com

Nachos picture from here: https://commons.wikimedia.org/....wiki/File:Goettanach

Vitamin Picture: https://commons.wikimedia.org/....wiki/File:Wyeth_Cent