The Scientific Method

The scientific method is a way that scientists seek to answer questions and explore observations of natural phenomena. After making observations, scientist use experimentation to search for cause and effect relationships. In other words, they design an experiment so that changes to one item cause something else to change in a predictable way. These changing quantities are called variables. An experiment usually has three kinds of variables: independent, dependent, and controlled.

The Independent Variable is the one that is changed on purpose by the scientist. In an experiment, there is only one independent variable. As the scientist changes the independent variable, he or she observes what happens. The Dependent Variable changes in response to the change the scientist makes to the independent variable. The dependent variable is sometimes called the responding variable because it responds to changes. These changes are measured and directly observed by the experimenter.

In many experiments it is important to perform a trial with the independent variable at a special setting for comparison with the other trials. This trial is referred to as a control group. The control group consists of all those trials where you leave the independent variable in its natural state. Controlled variables are those variables that we don't want to change while we conduct our experiment, and they must be the same in every trial and every group of trials.

To develop a scientific question, you must first make observations To develop a scientific question, you must first make observations. There are two types of observations; qualitative and quantitative. Qualitative observations are made with your five senses. You touch, taste, smell, see, and hear a natural phenomena. Quantitative observations are measurements you make with tools. Some of the measurements you can make are mass, volume, length, and temperature. Your observations should provoke curiosity about how something works, why something happens, and what causes something. Your observations need to be accurate and repeatable.

Once you have your observations and are considering questions your observations have provoked, now you begin to identify variables that might affect your observations. The scientist then raises a question about what (s)he sees going on. The question raised must have a “simple,” concrete answer that can be obtained by performing an experiment.

The hypothesis is a tentative answer to the question: a testable explanation for what was observed based on facts, observations, and available data. The key word is testable. That is, you will perform a test of how two variables (independent and dependent) might be related. This is when you are doing a real experiment. You are testing variables. The ultimate value of a formalized hypothesis is it forces us to think about what results we should look for in an experiment. Create a hypothesis statement using the If and then format. (If = the CAUSE - then = the EFFECT).

Remember to state your hypothesis in an If – Then statement Remember to state your hypothesis in an If – Then statement. If we do this, then this will happen. If the temperature of a gas is increased, then the volume will increase. If the length of a pendulum increases, then the period of swing will decrease. Look at the following scientific questions and think of If and Then hypothesis statements for each. Based on a need to conserve copper, a less expensive metal has been added to the alloy used to create a penny in recent years. Is it possible to detect when the composition of pennies changed from 1975 through 1995 based on the mass of the pennies? If the density of the new metal added to the penny alloy is less dense than copper, then the average mass of a penny would be less in the years the new metal was introduced. 2. Does adding a paper clip to a paper helicopter affect the amount of time the helicopter flies? If a small paper clip is added to a paper helicopter, then it will stay flying in the air the longest.

Now that you have come up with a hypothesis, you need to develop a procedure for testing whether it is true or false. This involves changing your independent variable and measuring the impact that this change has on the dependent variable. When you are conducting your experiment, you need to make sure that the only thing you change is the independent variable so that you are only measuring the impact of that single change. All the controlled variables must remain constant. Scientists run experiments more than once to verify that results are consistent. In other words, you must verify that you obtain essentially the same results every time you repeat the experiment with the same value for your independent variable. This insures that the answer to your question is not just an accident. Each time that you perform your experiment is called a run or a trial. The only way you can make sure that each run or trail is the same as the last trial is by writing a very specific set of directions describing exactly what you are doing. This is the procedure and it includes a list of materials to be used.

Every good experiment also compares different groups of trials with each other. Such a comparison helps insure that the changes you see when you change the independent variable are in fact caused by the independent variable. There are two types of trial groups: experimental groups and control groups. The experimental group consists of the trials where you change the independent variable. In many experiments it is important to perform a trial with the independent variable at a special setting for comparison with the other trials. This trial is referred to as a control group. The control group consists of all those trials where you leave the independent variable in its natural state.

Before beginning, prepare a data table to help you collect your data Before beginning, prepare a data table to help you collect your data. A data table will ensure that you are consistent in recording your data and will make it easier to analyze your results once you have finished your experiment. It is also important to take very detailed notes as you conduct your experiments. In addition to your data, record your observations as you perform the experiment. Write down any problems that occur, ideas that come to mind, or interesting occurrences. Be on the lookout for the unexpected. Your observations will be useful when you analyze your data and draw conclusions.

Take some time to carefully review all of the data you have collected from your experiment. Use charts and graphs to help you organize the data and patterns. Calculate statistical data like average, range, frequencies, and percents. A bar graph might be appropriate for comparing different trials or different experimental groups. It also may be a good choice if your independent variable is not numerical.

A line graph can be used if your dependent variable is numerical and your independent variable is time.

A circle graph is used to show how a part of something relates to the whole. This kind of graph is needed to show percentages effectively.

Stating a valid conclusion – The final step to complete the scientific method is to communicate a valid conclusion. A valid conclusion should include a claim statement about the solution to the problem you investigated. You should then state evidence that supports your claim. Your evidence comes from the quantitative data that you collected during your experiment. The evidence should be specific referencing numbers and measurements with units. Averages and percents from your data should be compared. Finally you explain your reasoning that lead you to your claim. The reasoning part of your conclusion is a justification that shows why the data counts as evidence to support your claim.

Scientific Method The