Identifying the variables of an experiment Independent Variables

Identifying the variables of an experiment

Independent Variables �Definition �The part of the experiment that is being changed on purpose to test the results of that change. �Example �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. �Key words in the purpose or question �Which… How much … How many … What type… How does… etc.

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

Controlled Variables �Definition �Something involved in the experiment that could affect the results �These need to be kept EXACTLY THE SAME for all test subjects! �Example �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 �Key words ------- none -------

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

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?