M anipulated V ariable (Independent variable)

Manipulated Variable (Independent variable) • the variable that is deliberately changed by the scientist. • “What is the scientist changing in this experiment?”

Responding Variable (Dependent variable) • the variable that changes as a result of the change in the manipulated variable. • “What is the scientist looking for or trying to measure?” • Or • “What is responding to the changes?”

controlled variables • all the variables that are kept the same so that any change in the responding variable can be attributed to the change in the manipulated variable • “What does the scientist have to do in order for this to be a fair test?”

Example #1

Does heating a cup of water allow it to dissolve more sugar?

Manipulative/Independent variable? • Independent variable

Manipulative/Independent variable • Temperature of the water measured in degrees Celcius

Dependent Variables?

Responding/Dependent Variables • Amount of sugar that dissolves completely measured in grams

Controlled • Stirring • Type of sugar • "More stirring might also increase the amount of sugar that dissolves and different sugars might dissolve in different amounts, so to insure a fair test I want to keep these variables the same for each cup of water."

Example #2 • Does fertilizer make a plant grow bigger?

Manipulative/Independent variable • Amount of fertilizer measured in grams

Responding/Dependent Variables • Growth of the plant measured by its height • Growth of the plant measured by the number of leaves

Controlled • Same type of fertilizer • Same size pot for each plant • Same type of plant in each pot • Same type and amount of soil in each pot • Same amount of water and light • Make measurements of growth for each plant at the same time

M anipulated V ariable (Independent variable)