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 Methods
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.
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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
involve 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 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.
Questioning Claims
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.
Theories
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 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. Wellaccepted theories are ones that are supported by different kinds of scientific
investigations often involving the contributions of many individuals from different
disciplines.