The Scientific Method
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How do scientists know so much?
How do they get to know more?
The Scientific Method: a structured
approach to problem solving and
answering questions.
Steps in Scientific Method
Make Observations
 Identify the Problem/Question
 State the Hypothesis
 Design a Controlled Experiment
 Observe and Measure Results (Collect data)
 Analyze Results and Draw Conclusions
 Report Results to Scientific Community
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An Early Scientific Theory
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Spontaneous Generation: a theory that
life can arise from nonlife.
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Why did people think this was true?
Mmmmm Maggots
Redi’s Experiment
Question: Can life arise from nonlife?
Set up experiment using the scientific method.
http://www.youtube.com/watch?v=WiGFoYBRYTA&feature=related&safe=active
http://www.youtube.com/watch?v=cQIbjhzBkU8&feature=related&safe=active
The Scientific Method
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My car won’t start
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Method
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Observe and Ask Questions
Infer and Form a Possible Answer (Hypothesis)
Design an Experiment to test Hypothesis
Collect and Analyze Data
Draw a Conclusion
Change Hypothesis if necessary and Retest
Step #1:
Make Observations
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Helps to define the problem for investigation
Step #2
Identify the Problem
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What is the question you want to ask?
Step #3
Form a Hypothesis
Hypothesis:
Create a scientific explanation (answer to
problem) that you can then test
Creating a Hypothesis
“If _____ then ______” statement
Ex:
If you add add fertilizer to a plant, then it will
grow taller
Step #4
Create a Controlled Experiment
Two identical groups are set up (control and
experimental)
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Allows you to isolate effects of one variable.
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Experimental Group: one variable
changes
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Control Group: no variables change,
(used as a basis for comparison)
Variables
Variables: factors that can change
(ex: light, time, amount of nutrients, growth)
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Independent Variable:
isn’t influenced by other
factors
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Dependant Variable:
“depends” on how the
other variable changes
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Cartoon Variables:
http://www.youtube.com/watch?v=x2606G
QmDqY&feature=related
Step #4
Collect Data
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Collect data using various research tools
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(ex: microscope, thermometer, ruler, scale)
Follow safety procedures
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Compile data in a useful form
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Ex: charts, tables and graphs
Types of Data to Collect
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Quantitative Data: measured “quantitiy”
(ex: length, mass, speed, volume, height)
 Use metric units of measurement
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Qualitative Data: descriptive “qualities”
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(ex: gorilla behavior, feather coloration)
Step #5
Analyze Data
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Analyze data to look for patterns or
relationships
Sample Size and Possible Sources
of Error
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Is it better to do an experiment with just a
few samples or many? Why?
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What possible sources of error might there
be ?
Graphing Properly
Space numbers in equal increments
 Plot points accurately
 Connect data points
 Give title to graph and label axis
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Graphing Variables
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Independent variable:
on “X” axis
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Dependant variable: on
“Y” axis
Step #6
Drawing Conclusions
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Does your data provide
evidence to support the
hypothesis?
or
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Should we revise
hypothesis and test again?
Scientific Method Loop
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What happens
when a hypothesis
is not confirmed?
Step #7
Report Observations
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Scientists need to report observations,
materials used and procedures to other
scientists.
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Needs to be stated so that someone else
could repeat exactly what you did.
Scientific Journals
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Different journals exist for different subfields of
science.
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Scientists read these journals to get new
information on recent developments in their fields
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Before it gets published, a research paper needs
to be reviewed by other scientists to make sure
that conclusions are supported by data.
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If your results are verified your hypothesis may
get accepted by scientific community
Experiment Example
Observation:
Marsh grass grows
taller in some places
Question:
Why do marsh grasses
grow to different
heights in different
places?
Inference:
Some environmental
factor is limiting grass
growth in a salt marsh
Hypothesis:
Marsh grass growth is
limited by amount of
nitrogen available in soil
Experimental
& Control groups
start out exactly
the same
The experimental group
changes one variable
Independent Variable:
nitrogen added
Dependant Variable:
growth of grass
The growth of grass
“depends” on nitrogen
being added
Data collected on height
of grass and size of
plants
Data confirmed that
additional nitrogen did
allow grass to grow
taller and larger than
control group
Theories and Laws
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Scientific Theories: explanations that apply to a
broad range of phenomena and are supported
by strong evidence and data.
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Ex: Germ Theory of Disease (Louis Pasteur)
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Diseases are often the effects of microscopic organisms
living inside a person.
Theory has lead to many effective treatments like antibiotics
But not all diseases are caused by germs
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Scientific Law: Statement that is always
true. (Ex: Law of Gravity)
Scientific Method Song
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http://singdancelearn.com/sciencesongs/scientific-method-song/
http://www.youtube.com/watch?v=eA86dYxrg4Q
http://www.youtube.com/watch?v=k2MhMsLn9B
0
http://www.youtube.com/watch?v=JcL7det0Ogs
Dance
http://www.youtube.com/watch?v=RmawlZCEeg
g&feature=related
The Scientific Method
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http://aspire.cosmicray.org/labs/scientific_method/sci_method
_main.html
Plant Experiment
 http://www.biologycorner.com/worksheets/
scientific_method_plant_exp.html
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Why does bread turn moldy?