the Scientific Method and the Scientist
his five senses,
man explores the Universe around him
and calls the adventure Science."
astronomer - 1948 A
Gk: Bios = life Logy = study of
the term biology was coined by Gottfried R. Treviranus in 1802.
Physics is the study of
atomic particles that interact by
a relatively simple set of rules that may be distilled
into predictive formulas.
Chemistry is a more complicated application of physics & its rules,
Biology, then could be a more complicated application of chemistry,
which also might be reducible to predictive physical formulas.
but as we shall learn, Biology's rules are messy and its molecular
interactions are almost impossible to faithfully predict.
Scientific Theories have 2 components:
1. one component describes PATTERNs observed in the natural world
2. other component identifies a PROCESS or MECHANISM responsible for the pattern
SCIENTIFIC METHOD* read this ......is a manner for investigating Nature
it's the methods by which scientists, collectively and over time, attempt to construct
an accurate, reliable, consistent, and non-biased representation of the natural world
a way of investigating the things (patterns) we observe around us,
a way of recording... the laws (mechanisms) that govern our physical world
a systematic study of patterns of living things & their processes...
it employs rigorous methodology and
it devises experiments to validate observations...
The scientific method was originated by the Greek philosophers [2600 years ago].
Thales (ca 590 b.c.) is considered the founder of the scientific method.
The prime question they asked was.. "what differentiates living from non-living".
" If we admit a priori that science is just the acquisition of knowledge that is,
building an inventory of all observable phenomena in a given disciplinary domain,
then, obviously, any science (may be called) empirical." Rene Thom, 1989
A scientist is one who
works in the trenches, seeking correct answers to a particular
problem, checking exhaustively for exceptions, guarding against mistakes and
preconceptions of an outcome, and avoiding personal bias.
"Science is what scientists do, and there are as many scientific methods as there
are individual scientists. The scientific method is what working scientists do,
not what other people do or even what they themselves may say about it."
Percy Bridgman, "On scientific method," in
Reflections of a Physicist, New York: Philosophical Library, 1955
Phrases by Mallery
SCIENTIFIC METHOD..... commonly includes a number of steps
description of a phenomenon or group of phenomena.
from previous studies or directly...
i.e., a gathering of the data...
observed: Bil 150students sitting in the back of the lecture hall, often fall asleep.
Begin to ask a Question: about the how's & why's of things you observe.
in scientific method: questions must be framed in measurable terms
Look for Answers to Your
others may have asked & answered the same type of question.
do literature searches: textbook, journal & internet articles...
reading other people's findings may lead to more interesting questions;
and help define or modify your question better.
Develop possible explanations:
a Hypothesis can be refuted (proven wrong) or falsified,
but a hypothesis can never be proven right,
and evidence can be collected to provide support for a hypothesis...
thus, there is often no proof in science, only 'disproof':
an example... Luis Alvarez (geophysicist) investigated assassination of JFK.
Premise: backwards motion of JFK's head as fatal bullet struck proves at
least one shot must have come from front (dual shooter idea),
since a shot from behind would only push head forward.
Hypothesis: "reflex of head requires a shot to have been fired from the front".
Experimental Alvarez showed shot could have come from behind
disproof: (laws of physics established a head can recoil backwards).
Conclusion: experiment does Not Prove shot was from behind,
but does Disprove presumption that a shot must have come from front.
when scientists publish they never say
but rather "results suggest..." or "results provide support for..."
hallmark of the scientific method is... DESIGNING an Experiment
Purpose of an EXPERIMENT...
to disprove a hypothesis or to evaluate an alternative hypothesis
experiments should meet certain criteria:
define the variables (see auxin experiment below)...
dependent variables: such as - number of parts, stem length, etc...
measurable & observable things; the variable modified by treatment
independent variable: only one variable to be manipulated, which may change
time, height, weight, age, sex, amount of hormone, etc..., the treatment
controlled variables: those kept constant and not allowed to change
all experiments must have a control... standard for comparison (a challenge)
example: relationship of
dependent variable: stem length (growth).
independent variable: auxin amount
¥ next and controlled variables: temp, humidity, day length, amount of fertilizer.
a big part of experimental design is materials & methods (the procedures)
based on previous published works, collegial suggestions, intuition, etc...
if auxin added to dwarf plants will stems to grow to normal height?
our experiments ought to include:
1. control: negative control: dwarf plants NOT given auxin
positive control: normal plants NOT given auxin *
2. proper concentration levels:
should not be too low (no effect detected) nor too high (toxic);
should be within physiological parameters of living cells
3. must be recordable: quantitatively measure length (mm)
4. must be replicable... redo several times, to be statistically valid
experiments ought to show consistent results
again and again, from test to test
Protocols & Terminology of the Scientific Methodology...
one often makes predictions about outcome of an experiment: that involves using...
Thinking... which includes
the formulation of an HYPOTHESIS,
(which is a tentative answer to a question) and doing experiments from which
may deduce a general answer to the hypothesis... often involves
nothing is accepted as fact, unless it is experimentally demonstrable
deductive reasoning... if...then logic
if all birds have feathered wings,
and a robin is a bird,
then robins have feathered wings.
predictions for our auxin experiment:
negative control: dwarf plants treated with water = remain short (dwarf)
positive control: normal plants treated with water = normal height
test treatment: dwarf plants treated with auxin = grow taller (normal)
Hypothetico-deductive methodology of scientific method also includes:
is the ability to deduce intuitive/creative principles...
objects fall to ground when dropped
thus, a force must act on the object... [gravity]
- results from earlier studies become initial observations of new studies
- everything that science "knows" - even long established theories -
are subject to reexamination as new information is collected.
- no endeavor of humankind rivals Science in its incremental progress
toward a more complete understanding of the observable world
- not all experiments are clear cut, scientific results must fit into known facts:
" all scientific knowledge is tentative, and open to challenge" cm
Collection & Interpretation data...
often draws upon previously known knowledge...
scientists fit new knowledge into framework of what they already know...
observations and measurements must always use same criteria...
plant height always measured from pot rim to shoot tip
variability must be estimated...
statistical analysis: some common statistical tests include...
t-test - compares the means of two groups
ANOVA - compares means of three (3) or more groups
chi square - compares how closely the observed or measured data
is to the expected results (ex: genetic crosses)
µ "Although concepts and ideas occupy a central place in the grand sweep of our under-
standing of the nature of the world around us, it is a mistake to imagine that they play a
greater role than tools and techniques in achieving scientific progress.
Few scientific revolutions are concept driven." [re: HGP].... John M. Thomas, 1994.
Organizing Data... raw data
is often expressed in tables and
tables: often used to emphasize numbers themselves, rather than a trend
figures: are graphs (trends), pictures, photos, diagrams (visuals)
line graphs - show effect of independent variable (X-axis) on
the dependent (measured) variable (Y-axis)
bar graphs - compare sets of data that may be discontinuous
i.e., maybe different groups
the best way to display your data often depends on what you want to
Examples*: aim is to show maximum growth rate is reached after several weeks
some fun experiments
The Twinkie Project...
[Rice University finals Week 1995]
¥ next 1.3 - An introduction to Graphing*.
It's easy to formulate an
It's hard to make a connection between cause and effect.
Draw a conclusion... if experimental outcomes match your predictions,
then your hypothesis is supported,
if not, then your hypothesis is negated.
Do your results agree with findings of other?
if not, do you know why not [different methods or species?]
Experimental Results are a tool: provide a sense of direction to experiments
do NOT let predictions affect your objectivity
do NOT make results fit your predictions (bias)
you may modify your hypothesis to fit the observed results...
modifications of a hypothesis help scientists gain assurance
that their explanations may be valid.
Negative results are often more important than positive ones:
¥ next Campbell - Concept Activity - Investigations - Chapter 1
1.4 - How Do Environmental Changes Affect a Population*
1.5 - How Does Acid Precipitation affect Trees*
In many scientific disciplines, the words "hypothesis", "theory", and
"law" can have different
connotations in relation to the stage of acceptance or knowledge about a group of phenomena.
A 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
Example: you discover that your car will not start. You may hypothesize...
"My flashlight doesn't work, because the battery is dead." your first hypothesis to test*.
A scientific theory or law represents a
hypothesis, or a group of related hypotheses,
which has been confirmed through repeated experimental tests over a long period of time.
('scientist') proposes a solution in the form of a 'hypothesis',
as a revelation of 'truth' that has been tested experimentally, again and again".
P. Haezrahi, 1970 paraphrased by chm 2002
How many of you believe there is
intelligent life elsewhere in the Universe ?*
IRONIC SCIENCE... (non-testable theories, but which are scientifically based)
Is there life elsewhere in the Universe
Greenhouse effect - its causes ? ...fossil fuel, deforestation?
Nuclear winter or meteor (...a cause dinosaurs mass extinctions? ice ages?)
Mount St. Helens, Gulf War... Earth-on-fire?
Complexity & chaos theory? makes it difficult to predict exactly
what is going to happen at any given time, in the present or the future.
chaos theory deals with the behavior of nonlinear dynamical systems that are characterized
by sensitivity to initial conditions. Examples include the atmosphere, the solar system,
plate tectonics, turbulent fluids, economies, and population growth.
ERROR in scientific experiments happens... & can have have several sources.
1. There is error intrinsic to the instruments used for measurements --> random error.
2. There is non-random or systematic error, due to factors which may bias the results.
No measurement, and therefore no experiment, can be perfectly precise...
A. Human error:
failure to follow procedures, failure to use the equipment properly,
failure to prepare solution correctly, measurements made by 2 researchers,
simple arithmetic errors, etc...
B. Another common mistake is to rule out or ignore data which do not support
the hypothesis... Humans have psychological tendency to find "something wrong",
with data, which does not support their hypotheses.
C. a scientist's personal bias can effect the outcome of an experiment...
most fundamental error is to mistake the hypothesis for an explanation of a
phenomenon, without performing experimental tests. Sometimes "common sense"
and "logic" can tempt us into believing that no test is needed.
...teacher can hit student in front to keep awake [bias]
Bias can be overcome... via open communication among members of the scientific
community because experimental tests are repeated by different scientists...
using different types of experimental setups.
Sharing your results...
the PUBLISH or
1. in a paper in a referred (peer-reviewed) journal publication + Open Access
2. at a poster session at a scientific meeting
3. via seminars at scientific meetings or symposia
Over a period spanning a variety of experimental tests (usually several years),
a consensus develops in scientific community as to which experimental results
¥ next have stood the test of time and become ----> THEORY.
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Last Update - 09/02/2008