Scientific Method Georgia CTAE Resource Network Instructional Resource Office To accompany curriculum for the Georgia Peach State Career Pathways April 2009, Kayla Calhoun & Dr. Frank Flanders

Objectives  List steps of the scientific method  Explain how different variables are used in an experiment  Contrast qualitative and quantitative data  Demonstrate knowledge of scientific method by performing an experiment

What is the scientific method? Principles and procedures for the systematic pursuit of knowledge involving recognition and formulation of a problem, collection of data through observation and experiment, and formulation and testing of hypotheses

Steps of the Scientific Method: 1. Ask a Question 2. Make Observations & Research Topic 3. Form a Hypothesis 4. Design & Perform an Experiment 5. Collect & Analyze Data 6. Draw Conclusions 7. Make Recommendations

Step 1: Ask a Question Recognize a problem and develop a question to be answered by experimentation

Step 2: Make Observations & Research Topic  Make observations  Do background research on the topic Find the best way to experiment Don’t repeat past mistakes

Step 3: Form a Hypothesis  After researching the topic, develop a hypothesis (an educated guess) about the outcome of your experiment  Basic format: “If I do this (independent variable), then this (dependent variable) will happen.”

Step 3 (continued): Variables  Independent variable (IV): the experimenter changes this variable; should only change one thing per experiment  Dependent variable (DV): value depends on the independent variable; its measure determines if hypothesis was correct or incorrect  All other conditions should remain constant in all trials so that any changes to the DV can be attributed to variation in the IV

Step 4: Design & Perform an Experiment  Procedure should be clear and easy to reproduce by others  Experimental group: independent variable is altered  Control group: standard of comparison; “no treatment” group  Only one factor is changed at a time in the experimental group, keeping all other conditions constant.

Step 5: Collect & Analyze Data  Collect measurements and analyze data  Procedure may be modified  Qualitative data relies on the senses and reveals changes in behavior  Quantitative data relies on measurable facts and figures  Repeat experiment a few times to maximize accuracy of results. Each replication is referred to as a trial.

Step 6: Draw Conclusions  Based on analysis of results, accept or reject the hypothesis Accept: test it again using a different variable. Reject: form a new hypothesis and go through the process again.

Step 7: Make Recommendations  Recommend further experimentation and possible improvements to the procedure.

Consistent results may lead to…  Theory: uses many experimental observations, can be applied to new situations, can be modified if new data appears; cannot be proven, only disproven  Law: confirmed in every experiment, creates true predictions for different situations, uniform, and universal

Pasteur’s Spontaneous Generation Experiment The following slides explain how Louis Pasteur used the steps of the scientific method to disprove the theory of spontaneous generation.

Pasteur’s Spontaneous Generation Experiment  Question: Can a nonliving substance (broth) produce living cells (bacteria)?  Observation: bacteria appeared in spoiled broth, and people thought the broth became bacteria, or produced it  Hypothesis: If cells (bacteria) arise from nonliving substances, they will appear in sterile broth.

Pasteur’s Spontaneous Generation Experiment  Experiment: Pasteur prepared a nutrient broth and exposed it to bacteria, contaminating it. He placed equal amounts of the broth into two long-necked flasks. One had a straight neck, and the other had a swan neck.

Pasteur’s Spontaneous Generation Experiment  Experiment: He boiled both flasks of broth to kill any existing bacteria (sterilization) and then left them at room temperature.

Pasteur’s Spontaneous Generation Experiment  Observation: Bacteria appeared only in the control flask with the straight neck; dust and condensed water accumulated in the swan necked flask.  Analysis: Dust carrying bacteria was able to fall into the straight-necked flask, but gravity forced it to stop in the neck of the swan-necked flask. Bacteria only contaminated the flask in which dust was able to enter.

Pasteur’s Spontaneous Generation Experiment  Conclusions: The shape of the flask affected the amount of bacteria in the broth; therefore, the broth did not produce the bacteria. The hypothesis of spontaneous generation is rejected.

Summary Steps of the Scientific Method:  Ask a Question  Make Observations & Research Topic  Form a Hypothesis  Design & Perform an Experiment  Collect & Analyze Data  Draw Conclusions  Make Recommendations