The word "science" is derived from the Latin word "scire," which
means knowledge. Today science is defined as a way of gathering
and organizing information (knowledge) about nature.
There are many branches of science. Some of these are:
1. biology--the study of life
2. zoology--the study of animals
3. botany--the study of plants
4. microbiology--the study of very small life forms, such as bacteria, viruses, molds, and fungus
5. anatomy--the study of structure. The study of the structure of the human skeleton would be a study in human anatomy.
6. physiology--the study of function. The study of the function of the heart would be a study of the physiology of the heart.
7. medical science--the study of health and disease. A physician is a medical scientist who practices medical science to cure disease or to help maintain good health. Practice means to use the principles of medical science.
8. psychology--the study of the human mind and human behavior. A clinical psychologist practices psychology to improve psychological well-being. An experimental psychologist tries to discover the principles which govern human behavior.
9. physics--the study of matter, motion and energy
10. chemistry--the study of elements and compounds
Many of the branches of science also have branches. Some of these are:
1. virology--a branch of microbiology. Virology is the study of viruses.
2. bacteriology--a branch of microbiology. Bacteriology is the study of bacteria.
3. Organic chemistry--a branch of chemistry. Organic chemistry is the study of the elements and compounds which compose living things. The word "organic" means living.
4. Inorganic chemistry--a branch of chemistry. Inorganic chemistry
is the study of the elements and compounds which compose
nonliving things. The word "inorganic" means nonliving.
Physical science is
the study of Physics and Inorganic Chemistry.
This means that Physical Science is the study of matter,
motion and energy--physics,
and the elements and compounds which compose nonliving
Still another way to define Physical
Science is the study of the nonliving parts of nature.
The one common element among all sciences is the use of the scientific method. The scientific method is the method used by scientists to solve problems. The steps in the scientific method are:
1. observation--something is observed about which a person becomes curious.
2. hypothesis--a tentative explanation or an educated guess as to why the observed event occurred. To be a good hypothesis it should be one that is testable. A hypothesis is testable if it is one that can be either proven or disproved by conducting an experiment. The plural of hypothesis is "hypotheses".
3. experiment--a way of testing a hypothesis. However, to increase the likelihood that your experiment will produce accurate information the experiment must be a controlled experiment. In a controlled experiment, all factors which influence the outcome of the experiment are kept the same except for the one whose effect is being studied. For example, if you were testing the hypothesis that a new fertilizer called WILDCATOLIZER would produce larger tomatoes than MIRACLE GROW, a controlled experiment might be designed as follows:
A. you should select genetically identical tomato seeds and randomly divide them into two groups. If different types of seeds were used, if there were observed differences in tomato size, it could be because one group of seeds were superior to the other. By using identical seeds, you would control a factor which could influence the outcome of the experiment.
B. The tomato plants grown with WILDCATOLIZER and the tomato plants grown with MIRACLE GROW must be planted in identical soils, in identical containers, given the same amounts of water, and exposed to the same amounts of sunlight. This type of control would reduce the chance that these factors produced any observed difference in tomato size. A controlled experiment such as this would give you more confidence that any observed difference in tomato size was in fact due to WILDCATOLIZER, and not due to some other factor.
C. By growing one group of tomato plants using WILDCATOLIZER
and comparing them to another group of tomatoes plants grown
with MIRACLE GROW, you increase the confidence in your results.
If you compared only a single tomato plant grown with
WILDCATOLIZER with a single tomato plant grown with MIRACLE
GROW, although you tried to control all factors which could
influence the outcome of the experiment, you may not have
actually done so. For example, the single seeds that you
selected may have looked alike, but one of them may have had a
genetic defect which could not be seen with the human eye.
Using groups helps to control for such unknown or undetectable
Variables: variables are things in an experiment which can vary. Because they can vary, they can effect the outcome of an experiment.
1. Manipulated variable, a.k.a. independent variable--this is the variable which the experiment is designed to test. In the above experiment, the manipulated variable would be WILDCATOLIZER. It is the experimental treatment.
2. Controlled variables--these are the factors which must be controlled in the experiment so that they will not effect the outcome. In the above experiment some controlled variables would be: soil, containers, amount of water, and sunlight.
3. Dependent variable--this is the variable which the experiment is
designed to measure. In the above experiment, the dependent
variable is the size of the tomatoes.
*In an experiment, a good way to think of the manipulated or
independent variable is to think of it as being the cause. A good
way to think of a dependent variable is to think of it as being the
Subjects: in a scientific experiment, the subjects of an
experiment are the things which are experimented upon. For
example, in the above experiment tomato plants were the subjects of
the experiment. However, the subjects of an experiment could be
almost anything, including experimental animals or even people.
Experiments often compare two groups of things. If two groups are compared in an experiment, the groups are given the following names:
1. experimental group--this is the group which is given the experimental treatment. In the above experiment, the experimental group is the group of tomato plants which received WILDCATOLIZER.
2. Control group, a.k.a. the comparison group--this is the group
which serves as a basis of comparison to the experimental group.
The purpose of having a control group in an experiment is to serve
as a basis of comparison. In the above experiment, the control
group is the group of tomatoes given MIRACLE GROW.
If the experimental and control groups are composed of people, such
as is usually the case in medical and psychological experiments, it
is important that the people not know in which of these groups they
serve. If the people know that they are in either the experimental
or the control group, they often react to this knowledge. This
reaction could make a difference in the experiment. To control for
this, scientist use what is called a blind experiment. A blind
experiment is one in which the subjects do not know if they are in
the experimental or control groups.
Placebo effect: All experiments which test drugs must control for
the placebo effect. If a scientist is experimenting to find the
effectiveness of a new sinus pill, and the experimental group is
given the new pill and the control group is given nothing, the
experimental group may expect something to result from taking the
pill. The control group would not expect anything. This
difference in what the two groups expect could make a difference in
the experiment. To control for this, the experimental group would
be given the sinus pill and the control group would be given a
placebo. A placebo is a fake pill which looks just like the sinus
pill, but is composed of sugar, or some inert substance. An inert
substance is a substance which is neutral or inactive. The placebo
is given so that the control group has the same expectations as the
experimental group. In a blind experiment, the subjects do not
know in which group they are serving, so they don't know if they
are getting the sinus pill or the placebo.
In many experiments it is necessary that the experimenter not know
which group is experimental and which is control. If the
experimenter should for some reason (like money, for example) wants
the experimental group to be superior to the control group, they
may either consciously or unconsciously treat the two groups
slightly different from each other. This difference in the way the
experimenter treats the two groups can make a difference. This is
called the experimenter bias effect. The experimenter bias effect
occurs whenever an experimenter either consciously or unconsciously
interjects their bias or expectations into the results of an
experiment. To avoid the experimenter bias effect, a double blind
experiment is performed. A double blind experiment is one in which
neither the subjects nor the experimenter know which group is
experimental and which is control. In a double blind experiment
the experimenter has an assistant which knows which group is
experimental and which is control. After the experiment is over,
the assistant tells the experimenter which group is which.
Repeatability: a good experiment is repeatable. Any other scientist should be able to repeat the experiment and expect to get similar results. If other scientist repeat an experiment and usually get similar results, the hypothesis may become a theory.
A theory is a well-tested hypothesis which experiments show to be
true most of the time. For example, biology has a theory known as
cell theory. Cell theory states that living things are composed of
cells. This is true most of the time. However, the fact that
viruses do not have cells, and appear to be alive, makes cell
theory a theory and not a law. A scientific law is a hypothesis
which has been proven to be true all of the time--without
exception. The law know as gravity has been proven to be true all
of the time.
Statistics: How much of a difference is really a difference? If
you flipped a coin 100 times, it should turn up heads half the time
and tails the other half. However, it seldom actually turns out
this way. If a person claimed to have psychokinesis (the ability
of the mind to directly effect matter) and attempts to use the
power of their mind to control the toss of a coin to make it turn
up heads, would you conclude that they really could control the
coin toss if they tossed it 100 times and it came up heads 51 times
and tails only 49? What if it turned up heads 60 times and tails
40 times? What if it turned up heads 90 times and tails only 10?
All of these outcomes could occur by chance. To determine what
that chance is, scientist use statistics.
If something can occur one time in 55 million, it probably will.
This is the probability that a person will win the Power Ball.
Over time, one ticket in 55 million will win the Power Ball. If a
scientist is conducting an experiment and the results can turn out
a certain way one time in 55 million, it just might occur.
Repeating the experiment will show if the results you obtained were
just lucky results. Statistics will also show this.
When scientists get the results of an experiment, they apply
mathematical procedures known as statistical procedures to their
results. Statistics are mathematical procedures that let
scientists know the probability that they obtained their
experimental results by pure chance alone. In general, if a
scientist could not expect their results to have occurred by chance
(luck) more that 5% or 1% of the time, they say that they obtained
a significant difference. However, even if a scientist gets a
significant difference, the experiment must be repeated again and
again to be sure that it wasn't just a lucky occurrence. Remember,
if something can happen 5% or 1% of the time, it probably will.
Only repetition gives scientists the assurance that their results
were not just luck alone.
1. Collected and recorded observations are referred to as data.
2. An inference is a logical conclusion drawn from available information.
3. Observation refers to information gathered through the senses or