Variables

Variables are things that vary and change

Types of Variables Variable: Any part of the experiment that can vary or be changed Control: A part of the experiment that is not being tested and is used for comparison

Types of Variables Independent (Manipulated) Variable: The part of the experiment that is changed or manipulated by the scientist Dependent (Responding) Variable: The part of the experiment that is affected by the independent variable (what is measured)

Example of Variables

Name the Variables What variables might affect the sprouting of a bean seed? What variables might affect the number of books sold by a door-to-door salesperson? What variables might affect the number of fish in a lake?

Name the Variables What variables might affect the speed of a runner in a 100-yard dash? What variables might affect the amount of fruit produced by an apple tree?

Assignment examples For each number: #1 IV DV CV

Variables? #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.

What was the independent variable? Ages of the students Different ages were tested by the scientist

What was the dependent variable? The time it took to put the puzzle together The time was observed and measured by the scientist

What was a controlled variable? Same puzzle All of the participants were tested with the same puzzle. It would not have been a fair test if some had an easy 30 piece puzzle and some had a harder 500 piece puzzle.

Name the Variables #2 The number of flowers on different kinds of bushes in a green house is recorded every week for 2 months. IV______________________________________________ DV______________________________________________ CV______________________________________________ #3 You water four sunflower plants with either pure water or different concentrations of water and salt solutions. After a two-week period, the height of the plants is measured. IV______________________________________________ DV______________________________________________ CV______________________________________________

Name the Variables #4 Three redwood trees are kept inside a greenhouse at different humidity levels for 12 weeks. One tree is left outside in normal conditions. Height of the trees is measured once a week. IV______________________________________________ DV______________________________________________ CV______________________________________________ #5 Pea plant clones are given different amounts of water for a three- week period. The first pea plant receives 400 milliliters. The second pea plant receives 200 milliliters. The third pea plant receives 100 milliliters. The fourth pea plant does not receive any water. The height of the pea plants is recorded daily. IV______________________________________________ DV______________________________________________ CV______________________________________________

Name the Variables #6 One tank of gold fish is fed the normal amount which is once a day, a second tank is fed twice a day and a third tank four times a day during a six week study. The fish’s body fat is recorded weekly. IV______________________________________________ DV______________________________________________ CV______________________________________________ #7 You decide to clean the bathroom. You notice that the shower is covered in a strange green slime. You decide to try to get rid of this slime by adding lemon juice. You spray half of the shower with lemon juice and spray the other half of the shower with water. After 3 days of “treatment” there is no change in the appearance of the green slime on either side of the shower. IV______________________________________________ DV______________________________________________ CV______________________________________________