VARIABLES

What is a variable?

A variable is something that affects something else. Or…

A variable can affect a system, an event or a process in some way.

A variable can cause a change.

Think of all the variables that will affect … Weather Conditions

Did you think of… Air temperature Air pressure Wind speed Clouds Humidity

Now list the variables for … Taste of pizza

Not all variables are the same.

When doing experiments, we must be able tell the different variables apart.

VARIABLE CIRCLE can help us tell the variables apart.

Here’s how you use it:

1. Draw a large circle.

2. Write EVERY variable you can think of inside the circle.

It is the only one that will change during the experiment. Choose the variable you want to find out about … test. It is the only one that will change during the experiment.

4. Take that variable OUT of the circle.

5. ALL variables still. inside MUST BE. KEPT THE SAME. IN YOUR 5. ALL variables still inside MUST BE KEPT THE SAME IN YOUR EXPERIMENT.

The variable you took out of the circle is the INDEPENDENT VARIABLE.

The independent variable is the ONE factor you will test in your experiment.

All the variables left inside MUST BE KEPT THE SAME during the experiment.

They are the Constants.

Let’s try an example.

of variables we made for the Go back to the list of variables we made for the taste of pizza.

Use the circle on your paper.

Write ALL the variables that affect the taste of a pizza INSIDE the circle.

(You might have more variables that those listed above.) Kind of dough How thick the crust is Kind of toppings Amount of toppings Kind of sauce Amount of sauce Kind of cheese Amount of cheese How long pizza was baked Age of pizza Temperature of pizza (You might have more variables that those listed above.)

Now we can choose ONE variable to test.

Let’s test the variable … Amount of cheese.

Use an arrow to “take it out” of the circle.

Kind of dough How thick the crust is Kind of toppings Amount of toppings Kind of sauce Amount of sauce Kind of cheese Amount of cheese How long pizza was baked Age of pizza Temperature of pizza Amount of cheese

Amount of cheese becomes the Independent variable.

When you set up your experiment, you will change the amount of cheese and see what difference it makes.

All of the other factors kept inside the circle MUST BE KEPT the SAME.

They are the Constants.

Independent Variable = amount of cheese So here’s what we have so far: Independent Variable = amount of cheese

Constants = all of the factors in the circle. (They MUST be kept the same in all the pizzas we use.)

There’s one more variable to learn about. It is called the Dependent Variable.

When you do your pizza experiment, you have to collect some data that let’s you know which pizzas people prefer.

So you might make pizzas with different amounts of cheese and then see which ones people chose to eat.

The number of pizzas eaten will be the Dependent Variable The number of pizzas eaten will be the Dependent Variable. It will show whether people prefer the taste of one pizza over another.

You can think of the Dependent Variable as the … “Data Done During” the experiment.

It is the data that you write down DURING the experiment.

The Dependent Variable depends on the other variables The Dependent Variable depends on the other variables. How many pizzas eaten depends on how much cheese they have.