Experiments

1. Experiments Definition: The scientific method of carefully controlling (2) variables/items, often in a lab, to demonstrate a known truth, examine the validity of a hypothesis, or determine the efficacy of something previously untried.

2. Experiments Independent Variable vs. Dependent Variable They are related!

3. Experiments Independent Variable=What the experimenter controls, or what is being manipulated. (How much sunlight the plants will get, how much of a drug will be given to participants, etc.)

4. Experiments Dependent Variable=It is “dependent” on the experimenter, or the I.V.. It is what will change when you change the I.V. (Ex: Your behavior (D.V.) will change depending on how much of a drug you are given. I.V.)

5. Experiments Which variable do you as the experimenter control? The I.V. or the D.V. ?

6. Experiments You want to see how plants grow under full sunlight (8 hrs. per day) vs. partial sunlight (4 hrs.per day) I.V ? D. V. ?

7. Experiments I.V=The amount of sunlight (the part you control) D. V. =The growth rate of the plants. (It “depends” on how much sunlight it is given.)

8. Experiments *Note: You can have more than one D.V. For ex., the growth rate of the plant is one D.V., but the height could be a second D. V.. Both are based upon the SAME I.V.

9. Experiments *Note: You normally do not have more than (1) independent variable. Why?

10. Experiments A controlled variable is anything else that could affect the D.V. (other than the I.V.) For example how much water you give the plant. (This must be “controlled” or equal for all plants so that we know it is not accounting for the change.)

11. Experiments Does one’s learning ability depend on one’s amount of sleep? If this were an experiment what would the I.V. & D.V. be?

12. Experiments What would some of the “controlled” variables be?

13. Experiments Definition of Experimental Group: This group is given something, or has a certain condition present. Give an example.

14. Experiments Definition of Control Group: This group is not given something, or does not have a certain condition present. The experimental and control group are identical in every other way.

15. Lets say you want to know the effect of excessive water drinking has on humans. You gather a group of people together and get them to drink a lot of water. This is the experiment group. What ever effects they display you might be inclined to attribute to excessive water drinking. HOWEVER, how do you know that all the symptoms they display are from drinking lots of water? Maybe some of the symptoms they display are totally unrelated to water and are the result of some other factor (like being together in an isolated group.) • Therefore, in order to separate excessive water symptoms from other symptoms you gather a second group of people together and place them in exactly the same environment as the first group EXCEPT you do not give them excess water. This is your control group. What ever differences there are between your experimental group and your control group are due solely to excess water.