On 9 Jan 2003 at 19:30, Bernard Barber, Ph.D. wrote:
> I have posted this site before, and now seems appropriate that it be posted
> again. I admit to being biased, being educated in Western Schools, Colleges
> and Universities, including Scandinavia, has provided me with the faith and
> belief in the Scientific Method.
>
> It seems to me that recent postings on our site suggest that even if there
> is a desire on the part of some, for more belief in non-traditional
> approaches to biological answers, it is very important that we all know just
> what is the scientific method.
>
Hi Bernie,
You probably forgot that the PARKINSN List won't be able to
accept your attachment...
It has to come through in the body as plain text (not HTML)
or not at all...
You have to copy to your clipboard and then paste it in like this...
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Introduction to the Scientific Method
The scientific method is the process by which scientists,
collectively and over time, endeavor to construct an accurate (that
is, reliable, consistent and non-arbitrary) representation of the
world. Recognizing that personal and cultural beliefs influence both
our perceptions and our interpretations of natural phenomena, we aim
through the use of standard procedures and criteria to minimize those
influences when developing a theory. As a famous scientist once said,
"Smart people (like smart lawyers) can come up with very good
explanations for mistaken points of view." In summary, the scientific
method attempts to minimize the influence of bias or prejudice in the
experimenter when testing an hypothesis or a theory.
I. The scientific method has four steps
1. Observation and description of a phenomenon or group of phenomena.
2. Formulation of an hypothesis to explain the phenomena. In physics,
the hypothesis often takes the form of a causal mechanism or a
mathematical relation.
3. Use of the hypothesis to predict the existence of other phenomena,
or to predict quantitatively the results of new observations.
4. Performance of experimental tests of the predictions by several
independent experimenters and properly performed experiments.
If the experiments bear out the hypothesis it may come to be regarded
as a theory or law of nature (more on the concepts of hypothesis,
model, theory and law below). If the experiments do not bear out the
hypothesis, it must be rejected or modified. What is key in the
description of the scientific method just given is the predictive
power (the ability to get more out of the theory than you put in; see
Barrow, 1991) of the hypothesis or theory, as tested by experiment.
It is often said in science that theories can never be proved, only
disproved. There is always the possibility that a new observation or
a new experiment will conflict with a long-standing theory.
II. Testing hypotheses
As just stated, experimental tests may lead either to the
confirmation of the hypothesis, or to the ruling out of the
hypothesis. The scientific method requires that an hypothesis be
ruled out or modified if its predictions are clearly and repeatedly
incompatible with experimental tests. Further, no matter how elegant
a theory is, its predictions must agree with experimental results if
we are to believe that it is a valid description of nature. In
physics, as in every experimental science, "experiment is supreme"
and experimental verification of hypothetical predictions is
absolutely necessary. Experiments may test the theory directly (for
example, the observation of a new particle) or may test for
consequences derived from the theory using mathematics and logic (the
rate of a radioactive decay process requiring the existence of the
new particle). Note that the necessity of experiment also implies
that a theory must be testable. Theories which cannot be tested,
because, for instance, they have no observable ramifications (such
as, a particle whose characteristics make it unobservable), do not
qualify as scientific theories.
If the predictions of a long-standing theory are found to be in
disagreement with new experimental results, the theory may be
discarded as a description of reality, but it may continue to be
applicable within a limited range of measurable parameters. For
example, the laws of classical mechanics (Newton's Laws) are valid
only when the velocities of interest are much smaller than the speed
of light (that is, in algebraic form, when v/c << 1). Since this is
the domain of a large portion of human experience, the laws of
classical mechanics are widely, usefully and correctly applied in a
large range of technological and scientific problems. Yet in nature
we observe a domain in which v/c is not small. The motions of objects
in this domain, as well as motion in the "classical" domain, are
accurately described through the equations of Einstein's theory of
relativity. We believe, due to experimental tests, that relativistic
theory provides a more general, and therefore more accurate,
description of the principles governing our universe, than the
earlier "classical" theory. Further, we find that the relativistic
equations reduce to the classical equations in the limit v/c << 1.
Similarly, classical physics is valid only at distances much larger
than atomic scales (x >> 10-8 m). A description which is valid at all
length scales is given by the equations of quantum mechanics.
We are all familiar with theories which had to be discarded in the
face of experimental evidence. In the field of astronomy, the earth-
centered description of the planetary orbits was overthrown by the
Copernican system, in which the sun was placed at the center of a
series of concentric, circular planetary orbits. Later, this theory
was modified, as measurements of the planets motions were found to be
compatible with elliptical, not circular, orbits, and still later
planetary motion was found to be derivable from Newton's laws.
Error in experiments have several sources. First, there is error
intrinsic to instruments of measurement. Because this type of error
has equal probability of producing a measurement higher or lower
numerically than the "true" value, it is called random error. Second,
there is non-random or systematic error, due to factors which bias
the result in one direction. No measurement, and therefore no
experiment, can be perfectly precise. At the same time, in science we
have standard ways of estimating and in some cases reducing errors.
Thus it is important to determine the accuracy of a particular
measurement and, when stating quantitative results, to quote the
measurement error. A measurement without a quoted error is
meaningless. The comparison between experiment and theory is made
within the context of experimental errors. Scientists ask, how many
standard deviations are the results from the theoretical prediction?
Have all sources of systematic and random errors been properly
estimated? This is discussed in more detail in the appendix on Error
Analysis and in Statistics Lab 1.
III. Common Mistakes in Applying the Scientific Method
As stated earlier, the scientific method attempts to minimize the
influence of the scientist's bias on the outcome of an experiment.
That is, when testing an hypothesis or a theory, the scientist may
have a preference for one outcome or another, and it is important
that this preference not bias the results or their interpretation.
The most fundamental error is to mistake the hypothesis for an
explanation of a phenomenon, without performing experimental tests.
Sometimes "common sense" and "logic" tempt us into believing that no
test is needed. There are numerous examples of this, dating from the
Greek philosophers to the present day.
Another common mistake is to ignore or rule out data which do not
support the hypothesis. Ideally, the experimenter is open to the
possibility that the hypothesis is correct or incorrect. Sometimes,
however, a scientist may have a strong belief that the hypothesis is
true (or false), or feels internal or external pressure to get a
specific result. In that case, there may be a psychological tendency
to find "something wrong", such as systematic effects, with data
which do not support the scientist's expectations, while data which
do agree with those expectations may not be checked as carefully. The
lesson is that all data must be handled in the same way.
Another common mistake arises from the failure to estimate
quantitatively systematic errors (and all errors). There are many
examples of discoveries which were missed by experimenters whose data
contained a new phenomenon, but who explained it away as a systematic
background. Conversely, there are many examples of alleged "new
discoveries" which later proved to be due to systematic errors not
accounted for by the "discoverers."
In a field where there is active experimentation and open
communication among members of the scientific community, the biases
of individuals or groups may cancel out, because experimental tests
are repeated by different scientists who may have different biases.
In addition, different types of experimental setups have different
sources of systematic errors. Over a period spanning a variety of
experimental tests (usually at least several years), a consensus
develops in the community as to which experimental results have stood
the test of time.
IV. Hypotheses, Models, Theories and Laws
In physics and other science disciplines, the words "hypothesis,"
"model," "theory" and "law" have different connotations in relation
to the stage of acceptance or knowledge about a group of phenomena.
An hypothesis is a limited statement regarding cause and effect in
specific situations; it also refers to our state of knowledge before
experimental work has been performed and perhaps even before new
phenomena have been predicted. To take an example from daily life,
suppose you discover that your car will not start. You may say, "My
car does not start because the battery is low." This is your first
hypothesis. You may then check whether the lights were left on, or if
the engine makes a particular sound when you turn the ignition key.
You might actually check the voltage across the terminals of the
battery. If you discover that the battery is not low, you might
attempt another hypothesis ("The starter is broken"; "This is really
not my car.")
The word model is reserved for situations when it is known that the
hypothesis has at least limited validity. A often-cited example of
this is the Bohr model of the atom, in which, in an analogy to the
solar system, the electrons are described has moving in circular
orbits around the nucleus. This is not an accurate depiction of what
an atom "looks like," but the model succeeds in mathematically
representing the energies (but not the correct angular momenta) of
the quantum states of the electron in the simplest case, the hydrogen
atom. Another example is Hook's Law (which should be called Hook's
principle, or Hook's model), which states that the force exerted by a
mass attached to a spring is proportional to the amount the spring is
stretched. We know that this principle is only valid for small
amounts of stretching. The "law" fails when the spring is stretched
beyond its elastic limit (it can break). This principle, however,
leads to the prediction of simple harmonic motion, and, as a model of
the behavior of a spring, has been versatile in an extremely broad
range of applications.
A scientific theory or law represents an hypothesis, or a group of
related hypotheses, which has been confirmed through repeated
experimental tests. Theories in physics are often formulated in terms
of a few concepts and equations, which are identified with "laws of
nature," suggesting their universal applicability. Accepted
scientific theories and laws become part of our understanding of the
universe and the basis for exploring less well-understood areas of
knowledge. Theories are not easily discarded; new discoveries are
first assumed to fit into the existing theoretical framework. It is
only when, after repeated experimental tests, the new phenomenon
cannot be accommodated that scientists seriously question the theory
and attempt to modify it. The validity that we attach to scientific
theories as representing realities of the physical world is to be
contrasted with the facile invalidation implied by the expression,
"It's only a theory." For example, it is unlikely that a person will
step off a tall building on the assumption that they will not fall,
because "Gravity is only a theory."
Changes in scientific thought and theories occur, of course,
sometimes revolutionizing our view of the world (Kuhn, 1962). Again,
the key force for change is the scientific method, and its emphasis
on experiment.
V. Are there circumstances in which the Scientific Method is not
applicable?
While the scientific method is necessary in developing scientific
knowledge, it is also useful in everyday problem-solving. What do you
do when your telephone doesn't work? Is the problem in the hand set,
the cabling inside your house, the hookup outside, or in the workings
of the phone company? The process you might go through to solve this
problem could involve scientific thinking, and the results might
contradict your initial expectations.
Like any good scientist, you may question the range of situations
(outside of science) in which the scientific method may be applied.
From what has been stated above, we determine that the scientific
method works best in situations where one can isolate the phenomenon
of interest, by eliminating or accounting for extraneous factors, and
where one can repeatedly test the system under study after making
limited, controlled changes in it.
There are, of course, circumstances when one cannot isolate the
phenomena or when one cannot repeat the measurement over and over
again. In such cases the results may depend in part on the history of
a situation. This often occurs in social interactions between people.
For example, when a lawyer makes arguments in front of a jury in
court, she or he cannot try other approaches by repeating the trial
over and over again in front of the same jury. In a new trial, the
jury composition will be different. Even the same jury hearing a new
set of arguments cannot be expected to forget what they heard before.
VI. Conclusion
The scientific method is intricately associated with science, the
process of human inquiry that pervades the modern era on many levels.
While the method appears simple and logical in description, there is
perhaps no more complex question than that of knowing how we come to
know things. In this introduction, we have emphasized that the
scientific method distinguishes science from other forms of
explanation because of its requirement of systematic experimentation.
We have also tried to point out some of the criteria and practices
developed by scientists to reduce the influence of individual or
social bias on scientific findings. Further investigations of the
scientific method and other aspects of scientific practice may be
found in the references listed below.
VII. References
1. Wilson, E. Bright. An Introduction to Scientific Research (McGraw-
Hill, 1952).
2. Kuhn, Thomas. The Structure of Scientific Revolutions (Univ. of
Chicago Press, 1962).
3. Barrow, John. Theories of Everything (Oxford Univ. Press, 1991).
Send comments, questions and/or suggestions via email to
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http://teacher.nsrl.rochester.edu/phy_labs/AppendixE/AppendixE.html
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cheers .... murray
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