EXPERIMENTAL SCIENCE PROJECTS:
An Intermediate Level Guide
David Morano, Assoc. Professor
Mankato State University
See original: http://www.isd77.k12.mn.us/resources/cf/SciProjInter.html
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There Are Different Forms of the Scientific
Method
Not all fields of science arrive at conclusions in the same way. The physical
sciences, like physics and chemistry, gather numerical data from which
relationships are derived, and conclusions are made. The more descriptive
sciences, like zoology and anthropology, may use a form of the method that
involves gathering of information by visual observation or interviewing. What is
common among all sciences, however, is the making of hypothesis to explain
observations, the gathering of data, and based on this data, the drawing of
conclusions that confirm or deny the original hypothesis.
Data for a physical scientist is numbers. The numbers are often plotted on
graphs. Graphs can be used to derive equations that can be used for making
predictions. Data, for an anthropologist, could be a recorded interview.
Interviews can be compared to other related information.
The information given below assumes you are doing an experimental science
project that uses the experimental method to gather data and test hypothesis.
What is the Experimental Scientific Method?
The steps listed below will help you systematically investigate observations
that can be tested with the experimental method. Not all questions can be dealt
with by the experimental scientific method. You must choose a question or
problem that can be formulated in terms of hypothesis that can be tested. Tests
done to check hypotheses are called experiments. To design a suitable experiment
you must make an educated guess about the things that affect the system you want
to investigate. These are called variables. As you do experiments, you will
record data that measures the effect of variables. Using this data you can
calculate results. Results are presented in the form of tables or graphs. These
results will show you trends related to how the variables affect the system you
are working with. Based on these trends, you can draw conclusions about the
hypothesis you originally made.
The existence of "cause and effect relationships" in nature is what
makes experimental science possible. Hypothesis can only be verified using the
scientific method described here if there is a cause and effect relationship
between the variables you have chosen and the system you are studying.
Experimental science is the search for cause and effect relationships in
nature. A hypothesis is your best guess at what this cause and effect
relationship is. Your conclusions will allow you to predict the result of future
cause and effect relationships. If you can do this, you can harness effects to
do things.
Initial Observation
You notice something, and wonder why it happens. You see something and wonder
what causes it. You want to know how or why something works. You ask questions
about what you have observed. You want to investigate. The first step is to
clearly write down exactly what you have observed.
Information Gathering
Find out about what you want to investigate. Read books, magazines or ask
professionals who might know in order to learn about the effect or area of
study. Keep track of where you got your information from.
Title the Project
Choose a title that describes the effect or thing you are investigating. The
title should be short and summarize what the investigation will deal with.
State the Purpose of the Project
What do you want to find out? Write a statement that describes what you want to
do. Use your observations and questions to write the statement.
Identify Variables
Based on your gathered information, make an educated guess about what types of
things affect the system you are working with. Identifying variables is
necessary before you can make a hypothesis.
Make Hypothesis
When you think you know what variables may be involved, think about ways to
change one at a time. If you change more than one at a time, you will not know
what variable is causing your observation. Sometimes variables are linked and
work together to cause something. At first, try to choose variables that you
think act independently of each other. At this point, you are ready to translate
your questions into hypothesis. A hypothesis is a question which has been
reworded into a form that can be tested by an experiment.
Make a list of your answers to the questions you have. This can be a list of
statements describing how or why you think the observed things work. These
questions must be framed in terms of the variables you have identified. There is
usually one hypothesis for each question you have. You must do at least one
experiment to test each hypothesis. This is a very important step. If possible,
ask a scientist to go over your hypothesis with you.
Design Experiments to Test Your Hypothesis
Design an experiment to test each hypothesis. Make a step-by-step list of what
you will do to answer each question. This list is called an experimental
procedure. For an experiment to give answers you can trust, it must have a
"control." A control is an additional experimental trial or run. It is
a separate experiment, done exactly like the others. The only difference is that
no experimental variables are changed. A control is a neutral "reference
point" for comparison that allows you to see what changing a variable does
by comparing it to not changing anything. Dependable controls are sometimes very
hard to develop. They can be the hardest part of a project. Without a control
you cannot be sure that changing the variable causes your observations. A series
of experiments that includes a control is called a "controlled
experiment."
Experiments are often done many times to guarantee that what you observe is
reproducible, or to obtain an average result. Reproducibility is a crucial
requirement. Without it you cannot trust your results. Reproducible experiments
reduce the chance that you have made an experimental error, or observed a random
effect during one particular experimental run.
Some Guidelines for Experimental Procedures
Obtain Materials and Equipment
Make a list of the things you need to do the experiment, and prepare them. If
you need special equipment, a local college or business may be able to loan it
to you. Another source of science materials are mail order supply houses such as
Edmund Scientific in Barrington, New Jersey (phone 1-609-457-8880 for a
catalog). Professional science supply houses are located in larger cities. They
will have just about anything you will need.
Do the Experiments and Record Data
Experiments are often done in series. A series of experiments can be done by
changing one variable a different amount each time. A series of experiments is
made up of separate experimental "runs." During each run you make a
measurement of how much the variable affected the system under study. For each
run, a different amount of change in the variable is used. This produces a
different amount of response in the system. You measure this response, or record
data, in a table for this purpose. This is considered "raw data" since
it has not been processed or interpreted yet. When raw data gets processed
mathematically, for example, it becomes results.
As you do experiments, record all numerical measurements made. Data can be
amounts of chemicals used, how long something is, the time something took, etc.
If you are not making any measurements, you probably are not doing an
experimental science project.
Record Your Observations
Observations can be written descriptions of what you noticed during an
experiment, or problems encountered. Keep careful notes of everything you do,
and everything that happens. Observations are valuable when drawing conclusions,
and useful for locating experimental errors.
Perform Calculations
Do any calculations needed from your raw data to obtain the numbers you need to
draw your conclusions. For example, you weighed a container. This weight is
recorded in your raw data table as "wt. of container." You then added
some soil to the container and weighed it again. This would be entered as
"wt. of container + soil." In the calculation section, do the
calculation to find out how much soil was used in this experimental run:
(wt. of container + soil) - (wt. of container) = wt. of soil used
Each calculated answer is entered into a table in a Results section.
Not all experiments need a calculation section. However, if you do not have
any calculations you may not be using the experimental scientific method. If you
have calculations to make, you probably are using the experimental scientific
method.
Summarize Results
Summarize what happened. This can be in the form of a table of processed
numerical data, or graphs. It could also be a written statement of what occurred
during experiments.
Often, mathematical equations can be made from graphs. These equations allow
us to predict how a change will affect the system without the need to do
additional experiments.
Draw Conclusions
Using the trends in your experimental data and your experimental observations,
try to answer your original questions. Is your hypothesis correct?
Other Things You Can Mention in the
Conclusion
Can I Trust My Results?
If you did not observe anything different than what happened with your control,
the variable you changed may not affect the system you are investigating. If you
did not observe a consistent, reproducible trend in your series of experimental
runs there may be experimental errors affecting your results. The first thing to
check is how you are making your measurements. Is the measurement method
questionable or unreliable? Maybe you are reading a scale incorrectly, or maybe
the measuring instrument is working erratically.
If you determine that experimental errors are influencing your results,
carefully rethink the design of your experiments. Review each step of the
procedure to find sources of potential errors. If possible, have a scientist
review the procedure with you. Sometimes the designer of an experiment can miss
the obvious.
Random Errors
If your measurement method is not the cause, try to determine if the error is
systematic or random. Random errors are more obvious. They result in
non-reproducible data that doesn't make sense. In this case, runs with the same
combination of variables, and even the control itself, cannot be duplicated.
Some randomness is always present in nature. No two measurements are exactly the
same. You must judge if the differences in your data can be explained by nature
operating normally.
A random error may be occurring because you are doing something differently
in each run. For example, you are not careful in cleaning your reaction vessels
and some of the chemicals are being carried over from the last experiment.
Scientists use various statistical tests to determine if the difference between
runs is due to randomness in nature, or to the way they are doing the
experiments.
Systematic Errors
Systematic errors are harder to find. Your data and results may look consistent
and reproducible. Here you may be doing something you are not aware of that is
causing all your measurements to be off the same amount. For example, if you
were not aware that a piece of your ruler had been cut off and now starts at
2" instead of 1", all your measurements would be one inch too long.
This is a systematic error because all your data is affected the same amount,
and in the same direction. One way to check for systematic errors is to run
experiments of a different design that should give the same answers. Scientists
often do different kinds of experiments to cross check their results. Another
way to locate errors is to have an independent investigator repeat your
experiments. Others should get the same results you did.
Linked Variables
Your results can be invalid if your variables are not independent of one
another, and you have not noticed this. Variables are independent if they
produce their effects separately from each other. In other words, changing one
variable does not affect changes produced by another variable.
Experimental
Errors