Experimental Design Guidelines
F
Question, Purpose, & Introduction (background information)
Question (title): This is the name of your experiment. It is a good idea to use your science
question as the title for your project.
Example:
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“How does temperature affect the amount of sugar that can dissolve into water?”
“How does amount of fertilizer affect plant growth?”
“Do bicycle fenders prevent water splash on a rider?”
Purpose: The purpose is a concise statement in complete sentences outlining the purpose of the
experiment. The purpose section of a lab is where you tell the reader your reason for doing the lab in
the first place and briefly summarize any relevant background information about the experiment,
including any relevant chemical equations and/or algebraic equations.
Example: if the research question is, “How does temperature affect the amount of sugar that can
dissolve into water?”
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The purpose of this experiment is to observe how different temperatures of water may affect
sugar absorption.
Introductory Paragraph – This section should be written in complete sentences and should
connect lab concepts to class content. The introduction should provide background information on
the history of the concepts tested, scientists, theories, and any laws tested in the experiment. Cite
Sources Used. The introduction should contain any prior knowledge on which the experiment is based
including an explanation of principles, definitions, experimental techniques, theories and laws.
(5-7 sentences)
Hypothesis
Hypothesis – a scientific prediction about the outcome of the experiment based on prior knowledge
and researched information. Based on your background information, write a statement that predicts
the outcome of the experiment. Many hypotheses are stated in an “if… then… because” statement
where the “if” statement pertains to the independent variable, the “then” statement pertains the
dependent variable, and the “because” statement uses your prior knowledge and background
information to explain why you predict the outcome.
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). In fact, many hypotheses are stated exactly like this: "If a
particular independent variable is changed, then there is also a change in a certain dependent
variable."
Example Hypotheses
Independent variable: temperature
Dependent Variable: the amount of sugar is the dependent variable
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"If the temperature of a cup of water is increased, then the amount of sugar that dissolves will
increase, because the faster moving water molecules are spread further apart than the
molecules in the cold water. With bigger gaps between the molecules in the hot water, more
sugar molecules can fit in between."
Independent variable: having fertilizer
Dependent variable: plant size
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"If a plant receives fertilizer, then it will grow to be bigger than a plant that does not receive
fertilizer, because fertilizer provides necessary nutrients that promote better plant growth."
Independent variable: having fenders is the independent variable
Dependent variable: how much water splashes on the rider
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"If I put fenders on a bicycle, then they will keep the rider dry when riding through puddles,
because fenders act as a protective barrier between the wheel and the rider."
Notice that in each of the examples it will be easy to measure the independent variables. This is
another important characteristic of a good hypothesis. If we can readily measure the variables in the
hypothesis, then we say that the hypothesis is testable.
Materials List & Procedure
Materials: Your materials list must be VERY complete. You need to indicate how much (quantity)
will be used in the experiment so you know what you will need. If you plan on arranging some of the
equipment into a more complex setup, draw and label a diagram showing the setup as well as
mentioning the equipment used. It’s also a good idea to leave a couple extra lines at the end of this
section so you can add more things that you may have forgotten when you started your lab.
Example: ALWAYS USE METRIC WITH AMOUNTS
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3 - 1 liter bowls
90 ml of water
3 - 8 cm x 8 cm squares of polyester in
different colors
3 - 8 cm x 8 cm squares of cotton in
different colors
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3 - 8 cm x 8 cm squares of nylon in
different colors
1 - Celsius thermometer
1 - Dry Stand
9 - Clothespins
1 - Notebook to record data
1 – Time
Procedure: This section is written in very clear numbered steps of how you plan to perform the
experiment such that the experiment could be repeated using you notebook. Each step should be
short (one phrase or sentence). You should complete at least three trials and include any safety
precautions that should be followed. The procedure must be written in the impersonal – 3rd person.
It’s also a good idea to leave a couple extra lines at the end of this section so you can add more
things that you may have forgotten when you started your lab.
Example Procedure:
1. Gather materials.
2. Tell the student to stand with both of their arms straight to the side of their body touching
their leg. The palms of the hands should be against their thigh.
3. State to the student that you will be holding the meter stick where it touches the ceiling and
without warning you will drop it and they are to catch it with their right hand between their
thumb and forefinger.
4. Place meter stick so that it is touching the ceiling with 100 centimeters at the top.
5. Drop the meter stick without warning.
6. Record the number on the meter stick where they caught it (use the lowest point).
7. If the student does not catch the meter stick the trial must be repeated.
8. Repeat the procedure four more times until the student has caught the meter stick a total of
five times with their right hand.
9. Record data after each drop.
10. Tell the student that you are now going to check their reaction time with their left hand and
they must catch the meter stick with their left hand in the same manner as before.
11. Repeat the procedure with the left hand four more times.
12. Record data after each drop.
13. Calculate averages for right hand distance and left hand distance and record in the data table.
14. Use the Conversion chart to convert distance into reaction time and find the averages for
each hand.
Results & Analysis
Results: This is the section where you write down all your raw data. It should consist of quantitative
(numerical) data arranged in tables, as well as qualitative (non-numerical) data written out in
sentences. The results section will most likely be long, so make sure you leave plenty of room. A
good rule of thumb when writing the results section is that if you are not sure if what you have seen
is a result, write it down. Your results section can never be too long.
Manipulated
Variable
Trial 1
Trial 2
Change 1
Change 2
Change 3
Control
(for comparison)
Analysis: This is where you explain the meaning of your
results and their significance. You should look for common
themes, trends, and other significant observations.
Include appropriate graphs, using the data from the
results. If calculations are required, they belong here. The
analysis section is the part of the lab where you explain
why your hypothesis is right or wrong, based on the data
you have taken. Like the results section, if you are in
doubt about whether or not to write something here,
include it.
When to use a line graph: Line graphs are used to track
changes over short and long periods of time. When
smaller changes exist, line graphs are better to use than
bar graphs. Line graphs can also be used to compare
changes over the same period of time for more than one
group.
When to use a bar graph: Bar graphs are used to
compare facts. The bars provide a visual display for
comparing quantities in different categories or groups. Bar
graphs help us to see relationships quickly. However, bar
graphs can be difficult to read accurately. A change in the
scale (y-axis) in a bar graph may alter one's visual
perception of the data. YOU MUST USE A PROPER SCALE.
When to use a pie chart: Pie charts are best to use when
you are trying to compare parts of a whole. They do not
show changes over time.
Trial 3
Average
Reflection & Conclusion
Reflection: the following questions should be answered using complete sentences at the end of
every experiment in your lab notebook. By answering these questions you are setting yourself up to
write a quality conclusion (which you will turn in).
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What was the main idea behind the experiment?
Was my hypothesis correct or incorrect?
How does the data support or oppose your hypothesis?
How does this relate to your life or what you are learning in class?
What would you like to test further? Explain why.
Were there any errors in your experiment? Explain.
Describe how your experiment ensures validity.
How could you increase the reliability of your experiment/study?
What don’t you understand?
Conclusion: The conclusion is a concise statement written in the impersonal (3rd person) past tense
that answers the experimental question. The basic organization of a conclusion follows the claim,
evidence, reasoning format.
Claim: the main idea
 A statement or conclusion that answers the original experimental question.
 Re-evaluate your hypothesis, were you wrong or right?
Evidence: what led you to make the claim?
 Scientific data & observations that supports the claim.
 The data needs to be appropriate and sufficient to support the claim.
Reasoning: explanation of the logic behind why the facts support the claim
 A justification that connects the evidence to the claim.
 Reasoning shows why the data counts as evidence by using appropriate and sufficient
scientific principles.
 Based on background information and concepts learned in class.
Other information to include:
 How to change the experiment for improved results.
 What did you learn
 If the hypothesis didn’t work, an explanation of what possibly went wrong. These should be
specific suggestions not general suggestions.
 List at least two possible errors in the lab, as well as ways to prevent those errors in the
future. The errors you mention should be errors that you can do something about, not
mystical errors that probably did not occur.