Laboratory Skills: Scientific Method
Vocabulary: bias, conclusion, control, control group, data, dependent variable, experimental design, experimental group, hypothesis, independent variable, peer feedback, peer review, problem, results, scientific method, theory, variable, variable group
Scientific explanations are developed using both observations and knowledge about what people already know. All scientific explanations are tentative explanations of phenomena and are subject to change. Good science is a combination of questioning, experiments, evidence, logical argument, ingenuity, and skeptical peer review. The scientific method and good scientific technique can be used in every day decision making, as well is in scientific investigation. Scientific literacy involves the use of science and it knowledge so that it can be applied in everyday life, particularly in relation to the health, commercial, and technological claims.
Scientific explanations are built by combining evidence that can be observed with what people already know about the world. This learning about the historical development of scientific ideas provides a better understanding of science, as well as the relationship between science and society. Personal values are also essential to making effective and ethical decisions about the application of scientific knowledge.
Developing a Research Plan
A procedure provides a description of how to organize a scientific experiment to test a hypothesis. The idea for research can be refined through library investigations, including the use electronic information such as e-mail and the internet, retrievals and reviews of scientific literature, and through peer feedback obtained from review and discussion of the problem, hypothesis, and procedure for experimentation before it is conducted.
Development of a research plan involves researching background information and understanding the major concepts in the area being investigated. Recommendations for the methods used for studying the problem, methods of study, technology selection and use, choice and use of proper equipment, and appropriate safety precautions should be included in the design of the experiment.
Scientists must follow certain steps in their attempt to solve problems. These steps are often referred to as the scientific method. The first step in the scientific method is to form a problem or question to solve. The formulation of the problem to be studied often requires as much work as the scientific experiment itself. The inquiry involved in the initial research of the problem involves asking questions and locating, interpreting, and processing information from a variety of sources. These other sources could include library information, information from other scientists, and the internet. When writing a scientific paper, this problem should be stated in the form of a question.
After the scientist has decided upon the problem to be researched, the second step of the scientific method is to form a hypothesis about the problem. This is an prediction of the possible outcome of an experiment based upon prior research and observation by the scientist. Hypotheses are widely used in science for determining what data to collect and as a guide for interpreting the data which is collected. The research plan for testing a hypothesis requires careful planning to avoid bias in this experiment. This plan should include repeated trials, large sample sizes, and objective data-collection techniques. As in deciding upon the problem to be researched, the development of a research plan involves researching background information and understanding the major concepts in the area being investigated. Recommendations for methodologies, use of technologies, proper equipment, and safety precautions should also be included in the design of the investigation. Well designed hypotheses are valuable, even if they turn out not to be true, because they may lead to further investigation and will direct the data collection activities in the experiment.
The third step of the experiment is the experimental design which tests the hypothesis. This procedure should clearly indicate the materials to be studied in the experiment and the measurements to be taken. There must be two groups included in the experimental procedure. The control group contains all the parts of the experiment except the factor being tested. The variable group contains all the factors of the control group as well as the one factor that is being tested. This is sometimes also called the experimental group. A well designed procedure contains only one variable. The control group acts as a basis to compare with the variable group.
There are two types of variables in an experiment. The independent variable is the variable which is changed or manipulated by the investigator. The dependent variable is the variable which is influenced by changes in the independent variable. This is what is measured in the experiment. The example which follows will illustrate some of the information involved in the design of a procedure.
The Scientific Method in Action
The following question about the scientific method appeared on the June 2001 New York State regents examination:
You are the head of the research division of the Leafy Lettuce Company. Your company is experimenting with growing lettuce using hydroponic technology. Hydroponic technology involves growing plants in containers of growth solution in a greenhouse. No soil is used. The growth solution that the company uses contains water, nitrogen, and phosphorus. The company wants to know if adding iron to this formula will improve lettuce growth.
- State a hypothesis to be tested in the new experiment
- State how the control group will be treated differently from the experimental group
- state what type of data should be collected to support or refute the hypothesis
- A good hypothesis relates the independent and dependent variables of the experiment together. In this experiment, a good hypothesis could be that the addition of iron to the growth formula will improve the growth of the lettuce. (Note that the hypothesis is phrased as a statement, not a question.)
The control group is not given the variable being tested. The experimental or variable group would receive the iron added to its growth solution, while the control group would not.
The type of data collected involves how the independent variable (the kind of growth solution) influences the dependent variable which is the growth of the lettuce. The experimenter would want to collect precise measurement data, such as how much more the lettuce grew in cm. or gained weight in grams.
The fourth step of the experiment is to organize the results or data collected. This may involved the use of data charts, graphs, tables, or drawings. When a variable is manipulated in an experiment, the data must include the changes in the independent and dependent variables. The scientist will then review these results. This often leads to new hypotheses being formed and additional scientific investigation.
The final step of an investigation may be to form a conclusion based upon the data. Using the trends in your experimental data and your experimental observations, the conclusion should try to answer the original problem. A conclusion should be able to assess the correspondence between the predicted result contained in the hypothesis and the actual results, and reach a conclusion as to whether the explanation on which the prediction was based is supported. No assumptions can be made about the results of the experiment past the one and only experimental factor that is being tested.
It is critical for the investigator is to communicate the results with others to allow for peer review of the investigation by other scientists. This can be done in a scientific journal, through the Internet, or by other means.
Peer Review and Repeatability of Experiments
One assumption of science is that other individuals could arrive at the same explanation if they had access to similar evidence. Scientists must make the results of their investigations public. The experimenter should describe the investigations in ways that enable others to repeat the investigations.
Scientists use peer review to evaluate the results of scientific investigations and the explanations proposed by other scientists. They analyze the experimental procedures, examine the evidence, identify faulty reasoning, point out statements that go beyond the evidence, and suggest alternative explanations for the same observations. Claims should be questioned if the data are based on samples that are very small, biased, or inadequately controlled or if the conclusions are based on the faulty, incomplete, or misleading use of numbers. The results of an experiment should be questioned if fact and opinion are intermingled, if adequate evidence is not cited, or if the conclusions do not follow logically from the evidence given. Accepting the results of any scientific inquiry involves making judgments about the reliability of the source and relevance of information obtained. Scientific explanations are accepted when they are consistent with experimental evidence and when they lead to accurate predictions about further extensions of the investigation.
Assessing Experimental Results
The results of a scientific experiment must be presented to the public and peers (other scientists) before they can be accepted. An assumption of science is that other individuals could arrive at the same explanation if they had access to similar evidence. The procedure used in conducting the experiment must be stated precisely enough to allow other scientists to perform the experiment and determine whether the results obtained are repeatable. The written report for public and peer study should describe the proposed explanation, literature reviewed, the research carried out, its result, and any suggestions for further scientific research.
Scientists use peer review to assess the results of scientific investigations and explanations proposed by other scientists. It is important the other scientists critique original research conducted by scientists in this manner. They analyze the experimental procedures, examine the data obtained in the experiment, and identify faulty reasoning in assessing the data. Peer review also leads to scientists pointing out any conclusions that go beyond the evidence obtained. They also may suggest alternative explanations for the same observations.
This peer and public discussion may lead to revisions of the explanation provided by the research and lead the scientist to additional research related to the original problem being investigated. Therefore, hypotheses are valuable, even if they turn out not to be true, because frequently they lead to further investigation.
The claims made in a scientific investigation should be questioned if the data are based on very small samples. Claims made by individuals having bias must be questioned. Bias means to have an opinion about the experimental results before the investigation which will lead to the misinterpretation or manipulation of the data obtained in the experiment. An improperly controlled scientific experiment must be questioned. The experiment should contain at least one clear control and one independent variable. The conclusions obtained in an experiment must be questioned if they are based on the faulty, incomplete, or misleading use of numbers. Fact and opinion must not be intermingled in a proper scientific experiment. The results of the experiment must cite adequate evidence and have its conclusion following logically from this evidence.
All scientific explanations are tentative and subject to change or improvement. Each new bit of evidence can create more questions than it answers. This leads to increasingly better understanding of how things work in the our world. When consistency is obtained in repeated scientific investigations of a problem the hypothesis becomes a theory and provides a set of ideas which explain a class of phenomena. A theory is then a framework within which observations are explained and predictions are made. Well-accepted theories are ones that are supported by different kinds of scientific investigations often involving the contributions of many individuals from different disciplines.