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The Scientific Method

The Scientific Method

Introduction: When a question arises, a good scientist does not haphazardly go about trying to find the answer. Instead, he or she will follow a pre-described set of steps to carry our a detailed and controlled experiment. This experiment will provide data that will allow the scientist to draw a conclusion about the question. This is called the scientific method.

This diagram below summarizes all the steps. As you can see, the scientific method is a prescribed pattern of steps that keep the scientist organized whenever they are conducting their research.

The first step in the scientific method is to present the problem. This could be a big question like, "How does ozone impact global warming?" or something a little smaller like, "What is the impact of red light on plant growth?" Both of these questions require experimentation in order to find the answer.

(It is important to note here that one test will not provide a definitive conclusion to the problem. In fact, science does not prove anything. When reports on television say that "studies proved..." they are indicating that all that needs to be known about the topic has been learned. Science does not work in this manner. There is always more to know. Data can suggest or data lead us to believe. However, data never proves!)

Once the problem has been asked, the researcher should go to the library to do background research. This will let them know if the question has ever been asked before and if so, what was discovered. This will provide them with a framework under which they can design their own study. It is at this point that the scientist will form a hypothesis. A hypothesis is based upon the background research and tells what the scientist thinks is going to happen during the experiment. It needs to be a testable statement. Phrases like, "I think it is going to rain today" or "I love my mom" are not hypotheses. "If plants are grown under red light, then they will not grow as tall as those grown under white light" is a testable statement.

The next step of the scientific method is to conduct the experiment. An experiment must be controlled and test only one variable at a time. Let's take the experiment mentioned above about the red light and plant growth. It is well known that plants grow tallest under white (natural) light. In the experiment, the researcher would have one setup where plants were growing under white light. This is called the control. Nothing will be done with these plants. In another setup, plants would be grown under red light. This is the experimental setup.

Now, it is important to only test one variable at a time. That which is being tested here is the light color. Therefore, all other conditions between the experimental and control setups needs to be the same. This includes the amount of water given, air temperature of the room, amount of food, and even the soil and size of the pot used. Only by keeping all these other factors the same will be be known if the red light is actually the cause of the difference in growth.

An experiment has two different variables. The first is called the independent variable. This is the factor that does not change. The other is called the dependent variable. This is the factor that does change. In the aforementioned experiment, the color of the light would be the independent variable and the height the plant grows is the dependent. Think of it this way - does the color of the light depend upon the height of the plant or does the height of the plant depend upon the color?

Once the experiment has been conducted, it is time to record and analyze the data. Data may be quantitative (numbers, such as the height the plant grew) or qualitative (observations, such as the condition of the leaves).

Since one trial is not enough to get a definitive answer, it is important for the researcher to repeat the experiment, often several times. The larger the sample size, the more accurate the results. If something is done once it is impossible to know if the outcome is the way it is supposed to be or just a fluke. By repeating the experiment the results become more valid.

Once the data from several trials have been collected, it is time to draw the conclusions about the experiment. As mentioned, there is no right or wrong answer to a scientific study. It is important for the researcher to support whatever conclusions they draw with data.

The final step of the scientific method is to publish the results. Imagine you have just discovered that plants grown in red light grew significantly taller than those in white light. Since this discovery contradicts everything that is already known about plant growth, it needs to be broadcast to the rest of the world. Writing scientific articles is the main way researchers get their findings out, but they may also write books or present at professional conferences.

Directions for this Lesson: Answer the practice questions and then watch the video to learn more about how scientists conduct research and answer questions.

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