A Nobel Prize winner in science once said that science is about “ordinary people doing ordinary things.” Scientists have a powerful tool that they can use to produce valuable, sometimes spectacular, results. The scientific method is a logical, systematic approach to the solution of a scientific problem. Steps in the scientific method include question, research, hypothesis, experiment, results, and conclusion.
Question The scientific method is useful for solving many kinds of problems because it is closely related to ordinary common sense. Suppose you notice that you always have lots of un-popped kernels in your bags of microwave popcorn. When you use your senses to obtain information, you make an observation. An observation can lead to a question: How can I get more of the kernels to pop? When you attempt to solve problems or ask questions about the world around you, then you are doing the first step of the scientific method. A good format is: How does ______affect ______or what is the relationship between ______and ______?
Research If you are trying to solve a problem or asking a question, the answer has often already been found. Therefore, researching the question can lead you to the answer. A scientist would look very silly wasting both time and money on an experiment that someone has already done and had the answer published. In the case of the popcorn one could research how to get more kernels to pop. If you find the answer then you are done.
If you come up with no answers then you might ask some questions which might help you find the answer. So you decide to research why popcorn pops and you find out that there is a drop of water in every kernel that boils, expands, and the kernel bursts open.
Good scientists use their resources and know where to most efficiently find answers to their questions. Textbooks and scientific journals are considered to be reliable sources of information. The Internet can also serve as a fast and reliable source of information, but you must be careful about where you get your information; anyone can post information. To judge you must consider the source. This same rule applies to articles in newspapers and magazines or news from television. Information from these types of sources becomes more reliable if the reporter specializes in science.
Hypothesis A hypothesis is a proposed answer or explanation to the question that can be tested. A hypothesis is often written as an If-Then statement. In the case of the popcorn your research led you an understanding of how popcorn is popped. After doing some thinking you come up the hypothesis that “If the popcorn is frozen while being stored, then a higher percentage of kernels will pop”. A hypothesis is not always able to be written as an If-Then statement, but in most cases it is.
Experiment An experiment is a procedure which is used to test a hypothesis. Experiments require that only one variable be manipulated at a time. In an experiment the variable that is manipulated / changed is called the independent variable. (Note: this is easy to remember by thinking that independent means by itself, therefore it is the one thing that is changed in the experiment) The independent variable is what you think is causing the problem or will answer your question. In an If-Then statement the independent variable is the section that follows the “If” part. In the case of your popcorn experiment you think that freezing the popcorn will cause a higher percentage of kernels to pop, therefore the temperature/freezing of the popcorn is the independent variable.
In order to evaluate the success of an experiment you must measure the success of the independent variable. The condition that responds to the independent variable is called the dependent variable. (Note: this is easy to remember because it depends on the independent variable) In an If-Then statement the dependent variable is the section that follows the “Then” part. In the case of your popcorn experiment you will freeze the popcorn then measure the percentage of kernels that pop, therefore the percentage of kernels that pop is the dependent variable.
If you can keep all other factors that can affect the experiment from changing, then you can relate any changes that occur in the dependent variable to the independent variable. The factors that do not change in an experiment are called constants. In the popcorn experiment these factors would include using the same microwave, type/brand of popcorn, time for cooking, and more.
In order to evaluate whether an experiment was a success you need something to compare it to. In other words you need to compare it to what would happen if you did not expose the independent variable. A control group is a part of an experiment which is not exposed to the independent variable. In your popcorn experiment you are measuring the percentage of kernels that pop after being frozen. However, in order to know if it makes any difference you must also know what percentage of kernels would pop with a normal bag of popcorn which is stored at room temperature. Therefore the room temperature bag of popcorn is the control group. An experimental group is the part of the experiment that is exposed to the independent variable. Therefore the frozen popcorn would be the experimental group. A controlled experiment is an experiment that contains both a control group and experimental group. Not all experiments are able to have a control group.
For the results of an experiment to be accepted, the experiment must produce the same result no matter how many times it is repeated, or by whom. This is why scientists are expected to publish a description of their procedures along with their results. Procedures should be written so that anyone with some knowledge of the topic could perform their procedure and obtain the same results.
Results In order to evaluate the success of an experiment scientists must obtain data. Data is the collection of scientific facts during an experiment. Data can be observations or measurements. Observations are obtained using the senses and organized so that they can be analyzed. The more observations that are made the more likely you will be able to correctly evaluate an experiment. Observations usually take the form of detailed diagrams or organized statements. In the popcorn experiment you might observe that the frozen popcorn begins to burn sooner or that its taste changes.
Measurements that are made during an experiment also serve as data. Data tables are created before the experiment so that no measurements are missed and are organized to be easily readable for their analysis. Data is often meaningless unless it is analyzed through mathematical calculations. Statistics are a mathematical way of evaluating data. This could include averages, medians, percentages, and many more. Scientists dissect every possible aspect of their data trying to find a cause, trend, or pattern in their experiment. In the case of the popcorn experiment one would need to count both the number of popped kernels and un-popped. These would be included into a data table. Then the percentage of kernels would be calculated by dividing the number of popped kernels by the total number of kernels.
Graphs serve to help analyze and make data that is collected in an experiment visual. By making data more visual a pattern or trend that may have gone unnoticed can become apparent. There are three main types of graphs: bar graphs, line graphs, and pie graphs. When making bar graphs and line graphs typically the dependent variable is on the y-axis (vertical) and the independent variable is on the x-axis (horizontal).
Bar graphs are typically used to compare groups or variables of an experiment. In the case of the popcorn experiment it might be helpful to see if the change that occurs is significant enough to draw a conclusion on its success. The graph might compare the percentage of kernels that popped between the frozen and unfrozen popcorn.
Line graphs are helpful for showing change of something when exposed to varying levels of the independent variable. An example of this might be comparing the percentage of kernels that popped when stored at many different temperatures (e.g. 0oC, 10oC, 20oC, etc). If a line graph produced a straight line this is described as linear and the variables are said to be directly proportional. In other words as one variable increases or decreases the other variable does the same. If a line graph produces a directional, smoothly curved line the variables are often inversely proportional. In other words as one variable increases or decreases the other variable does the opposite.
Pie graphs are helpful for showing the parts of a whole, with the whole being 100% of the group. In the popcorn experiment you might create a pie graph for both the frozen popcorn and unfrozen popcorn. Here the graph would show the number/percentage of popped and un-popped kernels.
Conclusion The conclusion is the most important part of the experiment. In a conclusion you must either accept or reject your hypothesis. You must explain why you accepted or rejected your hypothesis using the data that was collected and analyzed. This would include a summary of the data from the experiment (averages, patterns, sums, etc.). Conclusions often seem redundant because they rehash things that were already shown in the lab report, but they should be written so that someone could read them and be able to understand what was being tested in the experiment, what data was collected, what the results showed, and why the hypothesis is being accepted or rejected.
When a hypothesis must be rejected scientists sometimes will need to revise their hypothesis and change their experiment. This sort of thing happens all the time in science. It is OK to be wrong. The important part is that you have an idea on what went wrong or why your original idea didn’t work and learn from that experience.
If a hypothesis is accepted then a conclusion may attempt to provide a theory of why the phenomenon being investigated occurred. If a hypothesis is able to be repeated, it may be raised to a higher level of ideas, it may become a theory. A theory is a well-tested explanation of why a broad set of observations occur. In the case of the popcorn experiment you may form a theory that storing shelf foods, like popcorn, with water in them should be stored in freezers because the water is less likely to evaporate. Notice that the word because in the previous statement, provides the theory its necessary explanation for why it occurs. Before this theory were to be accepted in the scientific community it would need to be tested on many more experiments involving other shelf foods with water in them.
Theories can never be proved. This does not mean that they are unreliable. They are simply leaving open the possibility that a theory may need to be changed at some point in the future to explain new observations or experimental results.
Scientific Laws A scientific law is a concise statement that summarizes the results of many observations and experiments. It is important to note that laws do not attempt to explain why an event occurs. Rather they just describe a well-tested accepted pattern in nature that occurs in all instances. Gravity is an example of a law. The fact that objects are attracted to the earth or large bodies of mass is a pattern in nature that occurs no matter where you are in the universe.