Variables in a Science Experiment
The manipulated/ independent variable is the one condition the scientist changes during each trial in an experiment. If we look at the example to the right we notice that our manipulated /independent variable shows up in our question and our hypothesis.
It might help to understand what it means to manipulate something. Manipulate means to manage or use. In the case of the music experiment, we would manage or use the different types of music to see if they had an effect on test scores.
So, how does independent come in?
Independent means not needing or requiring any thing else. So the type of music isn't effected by any other element. No other factors in the experiment can change the music- the scientist gets to do that.
Q: What is the thing we are testing? What do we need to change to test our hypothesis?
A: Different kinds of music. The scientist will change the type of music for each trial.
Alright, how do manipulated and independent fit together?
The manipulated variable is independent of all other variables. In our example of music and test scores, the music is independent, because the music will not be changed by the test scores or the student. It is manipulated by the scientist.
Does Listening to Different Types of Music While Studying Effect Test Scores?
Let's look at some examples.
Example 1
A group of 5th grade students wants to know how different surfaces affect the speed of a rolling ball.They will change the type of surface. For example, they might use sand, gravel, grass, and concrete as the surfaces. The surfaces are independent of each other.
Wait! Gravel, sand, concrete and grass are 4 things!!! We are just supposed to change one thing!!!!
1 Category– 4 surfaces
In this case the scientist can test which surface will have the most friction and which one will have the least.
How Does Surface Friction Affect the Speed of a Rolling Ball
Example 2
A group of students wants to know how the amount of sunlight affects plant growth. They set up an experiment where they put 3 plants in direct sunlight, 3 plants in shade and 3 plants in a dark room. They are using different amounts of sunlight as their manipulated/ independent variable.
Example 3
A group of students are curious to know how heat affects dissolve rate of Alka-Seltzer. They decide to change the temperature of the water- hot, room temperature, and cold.
What is the manipulated/ independent variable in this scenario?
Did you pick the temperature of the water? The student scientists are manipulating or changing the temperature of the water in each trial.
Drawing coutesy of Madi C.
