1. Controlled Experiments and Variables A closer look at creating the perfect experiment!

2. Controlled Experiments an experiment that tests only one factor (variable) at a time, has a control group, and one or more experimental groups a - control group: A group in a scientific experiment where the factor being tested is not applied so that it may serve as a standard for comparison against another group where the factor is applied.groupfactor **Not all experiments will have a control group! b – experimental group: a group in a scientific experiment that is being tested

3. Example: Does eating breakfast in the morning help students do better in school? CONTROL GROUP: EXPERIMENTAL GROUP:

4. Variables a factor that changes in an experiment in order to test a hypothesis. The variable is often the one thing that is different between the control group (if applicable) and the experimental group.

5. Examples: The time it takes to run a kilometer depends on the amount of exercise a person gets. What are the two variables? 1. 2. ***Must include how each variable is measured or described!! The higher the temperature of water, the faster an egg will cook. 1. 2.

6. Manipulated Variable (MV A variable that is deliberately changed (i.e. you are changing it)

7. Responding variable The variable that may change as a result of changing the MV.

8. Examples: A- The more water you put on grass, the taller it will grow. MV— RV- B - More bushels of potatoes will be produced if the soil is fertilized more. MV— RV—

9. Control Variable(CV)— A variable that is NOT changed between the different groups. These variables are kept the same throughout the experiment. **There can be MORE than one CV

10. Examples: A - Students of different ages were given the same puzzle to assemble. The puzzle assembly time was measured. MV— RV – CV—

11. 1. Two groups of students were tested to compare their speed working math problems. Each group was given the same problems. One group used calculators and the other group did not have calculators. MV— RV— CV—

12. Variables 2. A study was done to find if different tire treads affect the braking distance of a car. MV— RV— CV—

13. 3. An experiment was performed to determine how the amount of coffee grounds could affect the taste of coffee. The same kind of coffee, the same percolator. The same amount and type of water, the same perking time, and the same electric source were used. MV— RV— CV—

14. 4. A study was done with an electromagnet system made from a battery and wire wrapped around a nail. Different sizes of nails were used and the number of paper clips that the electromagnet could pick up was measured. MV— RV— CV—