Scientific Method Pre-AP Biology

Definitions Accuracy-How close the results are to the accepted value. Precision-How close the results of multiple trials are to each other. Valid-an experiment that is trustworthy, scientific, “good”, results are accurate and precise.

Variables Variable-a characteristic that can be tested. Controlled variable (intervening variable)-the variable not being tested. (these variables need to remain the same in all groups.) Experimental variable-the variable chosen to be tested. Manipulated (Independent)-the variable being tested. It is usually something that can be determined before the experiment begins. Examples: time, temperature, etc. Responding (Dependent)-the variable that “responds” to the manipulated variable. It can only be determined after the experiment has been run.

Characteristics of a Good Experimental Design 1. Have a good representative sample: randomly selected and as large as possible (example: multiple plants, many animals, many people, etc.) 2. Only test one variable at a time. 3. Run multiple trials. (The more times the experiment is repeated the more valid your results will be.) 4. Follow all safety precautions. 5. Make sure to control any outside influences. 6. Express your results in table, chart, or graph form. 7. Include measurements if possible. 8. Include diagrams and/or photos if possible. 9. Make conclusions based on your results and data, not what SHOULD happen.

Scientific Method-How Scientists Work A. Designing an Experiment 1. Asking a Question 2. Forming a Hypothesis 3. Setting Up a Controlled Experiment 4. Recording and Analyzing Results 5. Drawing a Conclusion B. Publishing and Repeating Investigations C. When Experiments Are Not Possible: Use models or simulations D. How a Theory Develops: After repeated experiments with similar results

Designing an Experiment State the Problem Analyze Results Form a Hypothesis Draw a Conclusion Set Up a Controlled Experiment Publish Results Record Results

Plants in Color A student set up an experiment using plants and different colors of light. He used two plants under a blue light, two plants under a red light, two plants under a green light, two plants under a regular light bulb, and two plants under no light. He observed the plants for two weeks making sure they were watered properly, in the same kind of soil, in the same type of pot, and in the same location in the room. After two weeks, he counted the leaves and measured the height of the plant.

Instructions After Reading the Story: 1. What might be the hypothesis for this lab experiment?_____________________________________________________________________________________________________________________________________________________________________________ 2. What are some ways the student could compare the differences in the plants other than counting leaves and measuring the height? ____________________________________________________________________________________________ 3. What is the manipulated (independent) variable? ______________________ What is the responding (dependent) variable? _______________________

What are some controlled (intervening) variables that the student addressed? ________________________________________________________________________________________________________________________________________________________________________ What are some controlled (intervening) variables that the student should have addressed but didn’t? ________________________________________________________________________________________________________________________________________________________________________

What could the student have done differently that would have improved this experiment? (Hint: Look at the “Characteristics of a Good Experimental Design”) ________________________________________________________________________________________________________________________________________________________________________ What are some ways that the student could report his results? ______________________________________________________________________________________________________________________________

Design An Experiment Use the next four slides to plan your own experiment. Remember to include a title manipulated variable, responding variable, controls, how you will measure the results, and how you will report your results (graphs, charts, diagrams, etc.) You do NOT have to actually do the experiment! __________________________________________________________________________________________________________________________________________________________________________________________________________________

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