A VARIABLE is something to change in a experiment. The three types of variables are controlled, independent, and dependent.A controlled variable is something that you, the scientist control.An independent variable depends on nothing to change.A dependent variable is what you will use in Data Collection. It's form depends on the independent variable. For example:Students of different ages were given the same puzzle and timed to see how fast they could complete it.The independent variable would be their age: You NEED this to collect the data. The dependent variable would be the amount of time they took to complete the puzzle. You'd need to know this to write a statement.And the controlled variable would be that the puzzles were all exactly the same- that they each get the same puzzle so that they can set a tempo or base data.