Experimental Design

1. Experimental Design

2. Student Activity • Divide into groups of 3. • Using the shapes written on the board- Arrange the shapes on a piece of paper. • Design and write a procedure so that other groups will arrange shapes identical to the way your group did.

3. The Scientific Method: • State the Problem • Form a hypothesis • Set up a controlled experiment • Record and analyze results. • Draw a conclusion.

4. Designing an Experiment State the Problem Analyze Results Form a Hypothesis Draw a Conclusion Set Up a Controlled Experiment Publish Results Record Results Go to Section:

5. Hypothesis • educated guess • Example of an Educated Guess

6. Independent variable: • the variable which is manipulated • also called the manipulated variable • this is what you change • Example: Amount of water

7. Dependent variable • also called the responding variable • Changes because of what you did to it (independent) • This is the outcome • Example: Growth of the plant

8. Control variables • all other variables are kept the same in order to be sure which affected the outcome • Example: Amount of sunlight Temperature Others???

9. control/control set-up • used to compare results to • In testing if light effects the growth of a plant: control= no light

10. Spontaneous Generation • poof-it just occurs there • Keep in mind what Spontaneous generation is when discussing the experiments of the following scientists!

11. Francesco Redi Experiment on Spontaneous Generation OBSERVATIONS: Flies land on meat that is left uncovered. Later, maggots appear on the meat. HYPOTHESIS: Flies produce maggots. PROCEDURE Uncovered jars Covered jars Controlled Variables: jars, type of meat, location, temperature, time CONCLUSION: Maggots form only when flies come in contact with meat. Spontaneous generation of maggots did not occur. Several days pass Independent Variables: gauze covering that keeps flies away from meat Dependent Variable: whether maggots appear Maggots appear No maggots appear Go to Section:

12. Anton van Leeuwenhoek • Description: prepared lenses to magnify, found animalcules or tiny animals • Conclusion: Were animalcules alive or how did they come to exist?

13. John Needham • Description: See Spallanzani’s Experiment • He first did the experiment- Spallanzani repeated • Conclusion: Spontaneous generation occurred.

14. Lazzaro Spallanzani • Description: thought Needham did not heat the flasks enough • Conclusion: Spontaneous generation did not occur. Micro organisms not found in sealed flask after heating. Flask is open. Gravy is teeming with microorganisms. Gravy is boiled. Gravy is free of microorganisms. Flask is sealed.

15. Louis Pasteur • Conclusion: Hypothesis of spontaneous generation not correct! • Pasteurization Broth is teeming with microorganisms Broth is free of microorganisms for a year. Curved neck is removed. Broth is boiled.

16. Theory • Dictionary definition: speculation • People often use the word theory when they are really referring to a hypothesis. • Example: I have a theory about why the washing machine does not work. • Scientific definition: well tested explanation that unifies a broad range of observations. • Example: Theory of Plate tectonics, the theory of Evolution, and the Cell Theory