How Do Scientists Think? Scientific Method & Parts of an Experiment Copyright2003

Thinking like a scientist What makes the way that scientists think different from how you may think about the world around you? Scientists study the world and propose theories and outline natural laws about the world. Copyright2003

Theory vs. Natural Law A Theory is an explanation of how something works or why it happens the way it happens. Theories become more accepted as more experimental evidence is gather to support them as correct. No theory can ever be proven as 100% correct unless it is able to be directly observed as so. A Natural law is a description of a phenomenon that occurs the same way all the time. Since it’s behavior is so predictable It is often described with a mathematical formula. Copyright2003

If they were a scientist they use the scientific method. But anyone can formulate theories or explanations about the world. Why would anyone believe them? If they were a scientist they use the scientific method. Copyright2003

The Scientific method is: A systematic way of gathering evidence to support ideas and theories that help explain the natural world around them. Can you remember the steps of the Scientific Method? Copyright2003

Step 1: State the Problem What are you (or the experimenter) wondering about or trying to figure out? It is usually stated as a question containing words like: What, Why, How. Many problems are stumbled upon by simply observing the world around us. Copyright2003

Step 2:Research & Hypothesis An “Educated Guess” implies that you know something about the problem before you guess at it. You must do some research first. Hypothesis is a testable prediction based on research and observations. The hypothesis is what you (or the experimenter) think(s) is the answer to the problem. It sometimes sounds like a prediction of the answer to the problem. A good way of writing a hypothesis is: If…(a cause)…then…(an effect). Copyright2003

Step 3: The Experiment This is an organized process for testing the hypothesis Experiments must be reproducible so other scientist can try them for themselves. Experiments must have at least 4 parts. Copyright2003

Parts of the Experiment Variables are things that change. There are always two; The independent variable. Sometimes called the manipulated variable. The experimenter chooses one thing to do differently in the experiment. The dependent variable. Sometimes called the measured variable. This is the data that is being gathered or recorded. Copyright2003

Constants are all other things in the experiment that are kept the same all the time. A control is a standard for comparison. It is one of the trials in your experiment that you know the outcome for. You will usually use the control data to compare the other data you gathered in the experiment to it to see how much the dependent variable changed. Copyright2003

Step 4: Analyze Data Once the data has been collected it must be organized to find a pattern or trend. The data can be put into a graph so a pattern can be easily seen. Sometimes calculations are done with the data to get more information. Sometimes the outcome is simple compared to see the difference. Copyright2003

Step 5: Conclusions In a conclusion you should be sure to: State whether the hypothesis was a. supported b. rejected c. not able to either support or reject due to lack of a trend Give evidence from your experiment and data for your evaluation of the hypothesis as proof of your conclusions. You should include actual numbers from your data. Copyright2003

Practice Scenario Devon had a school project in which he was responsible for making bread. During the process of looking up the recipe he found out that little microorganisms known as yeast were responsible for making the gas that causes bread to rise and be fluffy. He didn’t believe this so he decided to conduct an experiment to see if bread would still be fluffy without yeast. Devon prepared two batches of bread. Both had the same amount of flour, same amount of sugar, same amount of water; the only difference was that Batch A had yeast added and Batch B didn’t. He marked the initial height of the dough on the outside of the bowl with a marker. He then covered both batches with plastic wrap, placed them in the same location on the countertop and measured how much each rose after 2 hours. He noticed that the bread with yeast added had risen and the bread without the yeast hadn’t risen at all. He was able to conclude that bread did require yeast in order to rise and be fluffy. Copyright2003

Modifying the Scientific Method to allow for past events Past events, by their nature of being in the past, have moved from real to abstract All that is in the past is in the memory or record To arrive at the truth of past events, the data must not be ignored or minimized. It must be coupled with observations made at the crime scene, crime lab, or morgue. The scientific method without modification to allow for past events will lead to mistakes. Copyright2003

Scientific Method (as it pertains to Forensic Science) Observe a problem or questioned evidence and collect objective data. Consider a hypothesis or possible solution. Examine, test, and then analyze the evidence. Determine the significance of the evidence. Formulate a theory based on evaluation of the significance of the evidence Kendall/Hunt Publishing Company