Variables and Graphing

Three types of Variables What is a Variable? Persons or objects that can be: manipulated controlled measured Three types of Variables Independent Dependent Control

Independent Variable – I.V. Something that is changed by the scientist What is tested What is manipulated Ex: fertilizer use on plants

Dependent Variable – D.V. something that might be affected by the change in the independent variable What is observed What is measured The data collected during the investigation Ex: How much the plants grew

Controlled Variable – C.V. Variable that is not changed Also called constants Allow for a “fair test” Also called “Standardized Variables”

***not on note sheet – add in!*** Control Group – C.G. ***not on note sheet – add in!*** In some experiments it is necessary to have a CONTROL GROUP This group DOES NOT receive the I.V. It is used as a comparison

Example 1 Students of different ages were given the same jigsaw puzzle to put together. They were timed to see how long it took to finish the puzzle. Name the independent, dependent, and control variable

Independent: ages of kids Answers: Independent: ages of kids Dependent: how long it took to complete puzzle Control: type of puzzle

The temperature of water was measured at different depths of a pond Example 2 The temperature of water was measured at different depths of a pond

Independent variable – depth of the water AnSWERS: Independent variable – depth of the water Dependent variable – temperature Controlled variable – thermometer

What things does a graph tell us? 1.

5 things every graph contains 1. Title – effect of IV on DV 2. Independent variable – x axis 3. Dependent variable – y axis 4. Scale – number increments 5. legend/key – short description about the graph