Variables

Control - things you need to keep the same:

• Amount of water - by soaking the toothbrush in water for 10 seconds
• Brand of eggs
• The time the eggs are soaked in coffee
• Strength of coffee
• Toothbrush
• Toothpaste

Test - what am I testing:

• Change between toothpaste and water
• You could also change between different toothpastes

Measured - what you are looking for:

• I am looking to see if toothpaste cleans the stains off your teeth better than toothpaste