I have a simple question about external variables. If I'm doing an egg drop experiment, and my teacher "chucks" it off of the roof in any way she feels like it, would that count as an external or independent variable?

I see it as the independent variable being the design of the egg drop contraption itself, and the dependent as being if it survives.

Ok, a few things here:

This is an egg drop experiment, so I'm assuming you are testing out different ways of protecting the egg.

The independent variable is what you want to change: This would be the type of protection you have on the egg

The dependent variable is what would be effected by the changes in the independent variable: which would be something like the integrity of the egg after it hits the ground. You'd have to measure that somehow.

There are two types of controlled variables: Internal and External.

Internal variables are within the scope of the experiment and can be controlled, whereas external variables are outside the scope of the experiment and we have no control over them.

Internal:

- Height of the drop

- Type of egg

- Person dropping

- How the egg is dropped

- Surface being dropped on to

External:

- The person designated to drop the egg is sick

- You run out of eggs to drop

- Somebody loses all the planning for the experiment

- The weather forces you to do the experiment inside versus outside

- The wind blows your egg off course, leading to it hitting the ground at an angle

So, the way your teacher "chucks" the eggs off the roof should be a controlled internal variable. The action should be done as consistently as possible to avoid an uncontrolled variable.