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Independent Variables Definition Example Key words in the purpose or question The part of the experiment that is being changed on purpose to test the results of that change. Question – How much light does a Boston fern plant need to grow the most in a month? Independent variable – The amount of light each plant gets. Which… How much … How many … What type… How does… etc. 2

Dependent Variables Definition Example Key words What you expect to change when the independent variable changes first Question – How much light does a Boston fern need to grow the most in a month? Dependent variable – how much the fern grows Effects … change … growth … rate of … most … greatest … 3

Controlled Variables Definition Example Key words Something involved in the experiment that could affect the results These need to be kept EXACTLY THE SAME for all test subjects! Question – How much light does a Boston fern need to grow the most in a month? Controlled variables – amount of water given to each plant, type of soil, temperature of room none

Variables Practice Copy each experiment question and then list the independent, dependent, and controlled variables. 5

Variables Practice What type of soil helps Boston ferns grow the most? Which type of fruit has the greatest amount of citric acid? What type of food should a sprinter eat to run a 100 meter dash the fastest? How does the loss of vision affect a person’s balance? Which type of wood has the greatest compression strength? Do athletes of different sports have different centers of gravity? 6