This intermediate level guide
contains information from Experimental
Science Projects: An Introductory Level Guide. Additional
material has been added to help distinguish between different
types of scientific studies. More details are also given about
the experimental scientific method, and the steps involved. Several
new sections have been added, most notably one that introduces
experimental errors. As you read about the various steps, you
may want to follow along with an example
To quickly jump to a section below
| Introduction | Science
Project Steps | Experimental
| What If My Science Project Doesn't
There Are Different Forms
of the Scientific Method
A confusing aspect of science is that not all fields of science
arrive at conclusions in the same way. The physical sciences,
like physics and chemistry, use experimental forms of the "scientific
method." The physical sciences do experiments to 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. The
difference is in what is considered data, and how data is gathered
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. Hence the distinction between the
exact sciences (physical sciences that use numbers to measure
and calculate results), and other sciences that use descriptions
and inferences to arrive at results. If you are not aware of
this difference, you could produce a written report for your
science project. Your project will then only show what you know
about something instead of experimentally answering questions
you have about observations you have made. 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
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
hypothesis 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.
This requires thought, information gathering, and a study of
the available facts relating to your problem. 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.
What Makes the Scientific
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.
What Is Experimental Science?
Experimental science is actually 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. Technology is the area that applies the findings of
the sciences to produce machines, or do things for us.
IN DOING AN EXPERIMENTAL SCIENCE PROJECT
The steps in the experimental scientific method as usually
presented are: Observation, Hypothesis, Controlled Experiment,
Conclusion. To actually do a science experiment, many more steps
are needed. The following more accurately reflects the course
of an actual experimental investigation.
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.
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
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
What do you want to find out? Write a statement that describes
what you want to do. Use your observations and questions to write
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
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
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
- Select only one thing to change in each experiment. Things
that can be changed are called variables.
- Change something that will help you answer your questions.
- The procedure must tell how you will change this one thing.
- The procedure must explain how you will measure the amount
- Each experiment should have a "control" for comparison
so that you can see what the change actually did.
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
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
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
(wt. of container + soil) - (wt. of container) = wt. of soil
Each calculated answer is entered into a table in a Results
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 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.
It is from calculations using recorded data that tables and
graphs are made. Studying tables and graphs, we can see trends
that tell us how different variables cause our observations.
Based on these trends, we can draw conclusions about the system
under study. These conclusions help us confirm or deny our original
hypothesis. 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. Advanced
levels of experimental science rely heavily on graphical and
mathematical analysis of data. At this level, science becomes
even more interesting and powerful.
Using the trends in your experimental data and your experimental
observations, try to answer your original questions. Is your
hypothesis correct? Now is the time to pull together what happened,
and assess the experiments you did.
Other Things You Can Mention
in the Conclusion
- If your hypothesis is not correct, what could be the answer
to your question?
- Summarize any difficulties or problems you had doing the
- Do you need to change the procedure and repeat your experiment?
- What would you do different next time?
- List other things you learned.
Try to Answer Related Questions
What you have learned may allow you to answer other questions.
Many questions are related. Several new questions may have occurred
to you while doing experiments. You may now be able to understand
or verify things that you discovered when gathering information
for the project. Questions lead to more questions, which lead
to additional hypothesis that need to be tested.
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.
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
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.
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.
If My Science Project Doesn't Work?
No matter what happens, you will learn something. Science
is not only about getting "the answer." Even if your
experiments don't answer your questions, they will provide ideas
that can be used to design other experiments. Knowing that something
didn't work, is actually knowing quite a lot. Unsuccessful experiments
are an important step in finding an answer. Scientists who study
extremely complex problems can spend a lifetime and not find
"the answer." Even so, their results are valuable.
Eventually, someone will use their work to find the answer. Are
you that person?