Scientific Method- Review
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 and processed.
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. 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 in this packet 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. 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.
Creating an Experimental Science Fair Project
For examples of all written parts of the project see the sample report (separate handout).
Your Science Fair Project Question
The question that you select for your science fair project is the cornerstone of your work. The research
and experiment you will be conducting all revolve around finding an answer to the question you are
posing. It is important to select a question that is going to be interesting to work on for at least a month
or two and a question that is specific enough to allow you to find the answer with a simple experiment.
A scientific question usually starts with: How, What, When, Who, Which, Why, or Where. Here are
some characteristics of a good science fair project question:

The question should be interesting enough to read about, then work on for the next couple
months.

There should be at least 3 sources of written information on the subject. You want to be able to
build on the experience of others!

For a science fair project, it is important to think ahead. This will save you lots of unhappiness
later. Imagine the experiment you might perform to answer your question. How does that
possible experiment stack up against these issues?

The experiment should measure changes to the important factors (variables) using a number that
represents a quantity such as a count, percentage, length, width, weight, voltage, velocity,
energy, time, etc. Or, just as good might be an experiment that measures a factor (variable) that
is simply present or not present. For example, lights ON in one trial, then lights OFF in another
trial, or USE fertilizer in one trial, then DON'T USE fertilizer in another trial. If you can't
measure the results of your experiment, you're not doing experimental science!

You must be able to control other factors that might influence your experiment, so that you can
do a fair test. A "fair test" occurs when you change only one factor (variable) and keep all other
conditions the same.

Is your experiment safe to perform?

Do you have all the materials and equipment you need for your science fair project, or will you
be able to obtain them quickly and at a very low cost?

Do you have enough time to do your experiment before the science fair? For example, most
plants take weeks to grow. If you want to do a project on plants, you need to start very early! For
most experiments you will want to allow enough time to do a practice run in order to work out
any problems in your procedures.

Have you avoided the bad science fair projects listed in the table at the end of the packet?
 Some science fair projects that involve human subjects, vertebrate animals (animals with a
backbone) or animal tissue, pathogenic agents, DNA, or controlled or hazardous substances,
need SRC (Scientific Review Committee) approval from your science fair BEFORE you start
experimentation. Now is the time to start thinking about getting approval if necessary for your
science project (see SRC).
Examples of good science fair project questions:
How does water purity affect surface tension?
Which material is the best insulator for the New England climate?
What is the effect of arch curvature on its load carrying strength?
How do various sugars affect the rates of yeast metabolism?
Making a Background Research Plan: How to Know What to Look For?
The place to start building your background research plan is with the question for your science fair
project. Let's imagine that you have asked this one:
Does drinking milk help decrease spiciness better than water or Pepsi?
After thinking about the Keywords —
Milk
Spiciness
Pepsi
Water
You might come up with these research questions —
Why do spicy foods taste hot?
How does the tongue detect spiciness?
How does one measure spiciness?
What causes spiciness to increase (or decrease)?
What are the properties and characteristics of spicy substances?
Where in the body does spiciness occur?
What is the composition of milk, Pepsi, and water?
What are the properties and characteristics of milk, Pepsi, and water?
These questions must be answered in order to begin planning the experiment!
Identifying Variables
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.
Variable vocabulary
Independent variable- the variable you are controlling or manipulating.
To insure a fair test, a good experiment has only one independent variable. As the scientist changes the
independent variable, he or she observes what happens.
Dependent variable- the variable you measure in the experiment.
The scientist focuses his or her observations on the dependent variable to see how it responds to the
change made to the independent variable. The new value of the dependent variable is caused by and
‘depends’ on the value of the independent variable.
Controlled variables- extraneous factors, possibly affecting the experiment, that are kept constant so as
to minimize their effects on the outcome.
An example of a control variable in an experiment might be keeping the pressure constant in an
experiment designed to test the effects of temperature on bacterial growth.
Experimental group- the group that receives the treatment
Control group- A group in an experiment that receives not treatment in order to compare the treated
group against a norm.
Example:
If you open a faucet (the independent variable), the quantity of water flowing (dependent variable)
changes in response--you observe that the water flow increases. The number of dependent variables in
an experiment varies, but there is often more than one.
If we want to measure how much water flow increases when we open a faucet, it is important to make
sure that the water pressure (the controlled variable) is held constant. That's because both the water
pressure and the opening of a faucet have an impact on how much water flows. If we change both of
them at the same time, we can't be sure how much of the change in water flow is because of the faucet
opening and how much because of the water pressure. In other words, it would not be a fair test. Most
experiments have more than one controlled variable. Some people refer to controlled variables as
"constant variables."
Making a Hypothesis
After having thoroughly researched your question, you should have some educated guess about how
things work. This educated guess about the answer to your question is called the hypothesis.
The hypothesis must be worded so that it can be tested in your experiment. Do this by expressing the
hypothesis using your independent variable (the variable you change during your experiment) and your
dependent variable (the variable you observe-changes in the dependent variable depend on changes in
the independent variable).
Examples
1. "Raising the temperature of a cup of water [temperature is the independent variable] will increase the
amount of sugar that dissolves [the amount of sugar is the dependent variable]."
2. "If a plant receives fertilizer [having fertilizer is the independent variable], then it will grow to be
bigger than a plant that does not receive fertilizer [plant size is the dependent variable]."
3. "If I put fenders on a bicycle [having fenders is the independent variable], then they will keep the
rider dry when riding through puddles [the dependent variable is how much water splashes on the
rider]."
Note: When you write your own hypothesis you can leave out the part in the above examples that is in
brackets [ ].
Not every question can be answered by the scientific method. The hypothesis is the key. If you can state
your question as a testable hypothesis, then you can use the scientific method to obtain an answer.
The keys to a good Hypothesis:
-
-
Written as a statement that predicts the outcome of the experiments
No pronouns used (No “I think” statements)
Mentions both the dependent and independent variables
Materials and Procedure
The materials list and procedure you will create will guide your experiment. However, during the
course of your experiment, you will most certainly need to modify both. Therefore, your final materials
list and procedure must consist of the modified materials list and modified procedure. The reason for
this is that when other scientists read the report they must be able replicate your experiment.
Note- The final written procedure on your display should be written in past tense and paragraph
form.
Some key ideas to include in your procedure:

Description and size of all experimental and control groups, as applicable 
A step-by-step list of everything you must do to perform your experiment. Think about all the
steps that you will need to go through to complete your experiment, and record exactly what will
need to be done in each step. 
The experimental procedure must tell how you will change your one and only independent
variable and how you will measure that change 
The experimental procedure must explain how you will measure the resulting change in the
dependent variable or variables 
If applicable, the experimental procedure should explain how the controlled variables will be
maintained at a constant value 
The experimental procedure should specify how many times you intend to repeat your
experiment, so that you can verify that your results are reproducible. 
A good experimental procedure enables someone else to duplicate your experiment exactly!
 Where will you conduct your experiment? You may need a lot of room for you experiment or
you may not be able to move your experiment around from place to place. If you are working
with human or animal subjects, you may need a location that is quiet. You will need to think
about these limitations before you start your experiment so you can find a location in advance
that will meet your needs.
Conducting the experiment

If you haven't already, obtain a notebook to record all of your observations during your
experiment. (see ”What makes a great science project logbook?”
http://www.sciencebuddies.org/science-fair-projects/project-laboratory-notebook.pdf )

Before starting your experiment, prepare a data table (in your science logbook) so you can
quickly write down your measurements as you observe them.

Follow your experimental procedure exactly. If you need to make changes in the procedure
(which often happens), write down the changes exactly as you made them. (in your science
logbook)

Be consistent, careful, and accurate when you take your measurements. Numerical measurements
are best.

Take pictures of your experiment for use on your display board if you can.
Data Analysis and GraphsTake some time to carefully review all of the data you have collected from your experiment. Use charts
and graphs to help you analyze the data and patterns. Did you get the results you had expected? What
did you find out from your experiment? Really think about what you have discovered and use your data
to help you explain why you think certain things happened.
Calculations and Summarizing Data
Often, you will need to perform calculations on your raw data in order to get the results from which you
will generate a conclusion. A spreadsheet program such as Microsoft Excel may be a good way to
perform such calculations, and then later the spreadsheet can be used to display the results. Be sure to
label the rows and columns--don't forget to include the units of measurement (grams, centimeters, liters,
etc.).
You should have performed multiple trials of your experiment. Think about the best way to summarize
your data. Do you want to calculate the average for each group of trials, or summarize the results in
some other way such as ratios, percentages, or error and significance for really advanced students? Or, is
it better to display your data as individual data points?
Do any calculations that are necessary for you to analyze and understand the data from your experiment.
Use calculations from known formulas that describe the relationships you are testing. (F = MA , V = IR)
Pay careful attention because you may need to convert some of your units to do your calculation
correctly. All of the units for a measurement should be of the same scale– (keep L with L and mL with
mL, do not mix L with mL!)
Graphs
Graphs are often an excellent way to display your results. In fact, most good science fair projects have at
least one graph.
Generally, you should place your independent variable on the x-axis of your graph and the dependent
variable on the y-axis.

Be sure to label the axes of your graph— don't forget to include the units of measurement
(grams, centimeters, liters, etc.).

If you have more than one set of data, show each series in a different color or symbol and include
a legend with clear labels.

Different types of graphs are appropriate for different experiments. These are just a few of the
possible types of graphs:
A bar graph might be appropriate for comparing different trials or different experimental groups. It also
may be a good choice if your independent variable is not numerical. (In Microsoft Excel, generate bar
graphs by choosing chart types "Column" or "Bar.")
A time-series plot can be used if your dependent variable is numerical and your independent variable is
time. (In Microsoft Excel, the "line graph" chart type generates a time series. By default, Excel simply
puts a count on the x-axis. To generate a time series plot with your choice of x-axis units, make a
separate data column that contains those units next to your dependent variable. Then choose the "XY
(scatter)" chart type, with a sub-type that draws a line.)
An xy-line graph shows the relationship between your dependent and independent variables when both
are numerical and the dependent variable is a function of the independent variable. (In Microsoft Excel,
choose the "XY (scatter)" chart type, and then choose a sub-type that does draw a line.)
A scatter plot might be the proper graph if you're trying to show how two variables may be related to
one another. (In Microsoft Excel, choose the "XY (scatter)" chart type, and then choose a sub-type that
does not draw a line.)
Writing a Conclusion (also known as the discussion)
Your conclusions will summarize whether or not your science fair project results support or contradict
your original hypothesis. If you are doing an Engineering or Computer Science programming project,
then you should state whether or not you met your design criteria. You may want to include key facts
from your background research to help explain your results. Do your results suggest a relationship
between the independent and dependent variable?
If Your Results Show that Your Hypothesis is False
If the results of your science experiment did not support your hypothesis, don't change or manipulate
your results to fit your original hypothesis, simply explain why things did not go as expected.
Professional scientists commonly find that results do not support their hypothesis, and they use those
unexpected results as the first step in constructing a new hypothesis. If you think you need additional
experimentation, describe what you think should happen next.
Scientific research is an ongoing process, and by discovering that your hypothesis is not true, you have
already made huge advances in your learning that will lead you to ask more questions that lead to new
experiments. Science fair judges do not care about whether you prove or disprove your hypothesis; they
care how much you learned.
Key info for Conclusions:
 Summarize your science fair project results in a few sentences and use this summary to support
your conclusion. Include key facts from your background research to help explain your results as
needed.

State whether your results support or contradict your hypothesis. (Engineering & programming
projects should state whether they met their design criteria.)

If appropriate, state the relationship between the independent and dependent variable.

Summarize and evaluate your experimental procedure, making comments about its success and
effectiveness.

Suggest changes in the experimental procedure (or design) and/or possibilities for further study.