2. The Scientific Method How to design a good experiment

3. What is science? Science is a process that is used to explore observations and to answer questions The scientific method involves a series of steps that scientists use to investigate a natural occurence

4. Problem/Question Observation/Research Formulate a Hypothesis Design an Experiment Collect and Analyze Data Conclusion Communicate the Results

5. Steps of the Scientific Method Problem/Question 1. Problem/Question: Develop a testable question that can be answered by experimentation.

6. Steps of the Scientific Method Observation/Research 2. Observation/Research: Make observations and research your problem or question.

7. Do you remember the next step?

8. Steps of the Scientific Method Formulate a Hypothesis 3. Formulate a Hypothesis: Predict a possible answer to the problem or question. Example: If soil temperatures rise, then plant growth will increase, because plants photosynthesize more in hotter environments.

9. Steps of the Scientific Method Experiment 4. Experiment: Develop and follow a detailed procedure that explains each step exactly. Include a materials list.

10. Steps of the Scientific Method Collect and Analyze Data 5. Collect and Analyze Data: Run several trials of the experiment Analyze using tables, graphs, and photographs.

11. Steps of the Scientific Method Conclusion 6. Conclusion: Accept or reject the hypothesis and discuss reasons for results Include analysis of data and possible improvements to the procedure.

12. Steps of the Scientific Method Communicate the Results 7. Communicate the Results: Be prepared to present the project to an audience. This is how scientists “check” each others results

13. Designing An Experiment – Variables 3 types of variables… Independent Variable – the variable that is changed by the scientist –The one being tested or manipulated –We know the value of this variable before running the experiment Ex. – does the drop height of a superball affect the bounce height? We know the drop height we will use.

14. 3 Kinds of Variables Dependent Variable – the variable that might be affected by changing the independent variable –It is “what you measure” –We do not know the value of this variable without running the experiment Ex. – does the drop height of a superball affect the bounce height? We do not know the bounce height before we start.

15. 3 Kinds of Variables Controlled Variable – variables that are not changed at all –Things that “could” change the results –They should be kept the same for every group –Also called constants, they allow for a “fair test” –Ex. – does the drop height of a superball affect the bounce height? The superball should not change during the experiment.

16. For Example…Identify the IV, DV and a controlled variable (constant) 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. –IV… different ages of students –DV… time to finish puzzle –Constant… same puzzle every time

17. Another Example…Identify the IV, DV and a controlled variable (constant) An investigation was done with an electromagnetic system made from a battery and wire wrapped around a nail. Different sizes of nails were used. The number of paper clips the electromagnet could pick up was measured. –IV… Size of the nail –DV… number of paper clips picked up –Constant… Battery, type of wire, type of nail

18. Designing an Experiment – Control Group The control group is the group that serves as a standard for comparison. –Usually a “no treatment” group –Everything is exactly the same EXCEPT the independent variable “no IV” or “normal IV” ALL EXPERIMENTS MUST HAVE A CONTROL GROUP!!!

19. Examples of control groups How does fertilizer affect the growth rate of plants? –we set up an experiment testing different amounts of fertilizer on different plants & measuring the growth (height) of the plants: Control group –Plants that get no fertilizer

20. Examples of control groups How does amount of exercise affect student heart rates? –we set up an experiment testing different lengths of time of exercise (minutes) on the heart rate of students: dependent variable (Y-axis)? –heart rate independent variable (X-axis)? –minutes of exercise Control group –A group of students that does no exercise

21. Experimental Design: Repeatability A successful experiment is validated by repeating it. –By you or by others (directions must be exact and very specific) –Do several trials of your experiment It is also important to have many subjects that you are testing on in each group –A minimum of 10 per group is a good round # to remember –This way if one of your plants dies, you don’t conclude that water kills plants!

22. Scientific Bias Bias – anything that creates a pre- conceived idea about the outcome of an experiment. –A statement by a teacher (HR should rise with drugs) –The group that funds the research (Tobacco company funds a study on the effects of nicotine on rats) Medical researchers often use a “double- blind” strategy to eliminate bias –Neither the researchers or the subjects know which pill the subjects are taking, the real drug or the placebo. Placebo = sugar pill = no effect