The Scientific Method
• There is simply no fixed set of steps that
scientists always follow, no one path that
leads them unerringly to scientific
“The Scientific Method”
1) Question or Problem
2) Hypothesize
3) Predict Consequences 4) Experiment
5) Interpret Experimental Results
• An experiment is a test
used to determine if
there is evidence to
support a hypothesis
What is a hypothesis?
• A hypothesis is a guess or prediction about
a phenomenon.
• Hypotheses can be stated as positive or
• The “null” hypothesis predicts that there
will be NO difference between experimental
Write your own hypothesis
• Write your prediction for the outcome of the
radish seed experiment
• You should also provide a REASON.
– Why do you think the experiment will turn out
the way it will?
What is a theory?
• A theory is an explanation that has a very
large amount of evidence to support it.
• A fact is an observation about nature. A
theory is an explanation. So a theory can
never “become” a fact.
Experiment Titles
• Usually, experiments are titled in a format
like this:
• “The Effect of _______ on _________”
• Sample title: “The Effect of Light on
Growth of Radish seeds”
Experimental variables
• The ONE factor that you cause to be
different between experimental groups is
the MANIPULATED variable (also called
INDEPENDENT variable).
• Sample: In the radish seed experiment, the
manipulated variable is”Amount of Light”
Experimental variables
• The factor that you measure as the outcome
of the experiment is called the
RESPONDING variable (also called
DEPENDENT variable)
• In the radish seed experiment, the
responding variable is ___________.
• The responding variable is LENGTH of
STEM, measured in millimeters.
• All other factors in the experiment must be
controlled so they are the same for all
• Examples of constants in radish seed
• Type of Petri dish type of seed
• Number of seed
paper towel
• Water, Location
• Obtain a flexible plastic ruler and measure
the length of the radish seeds today in
• Record your data and your partner’s data in
the data table.
Observing plant growth:
• Take bean and pea seeds and put them in
containers of soil under our light source.
• Water them consistently.
• Each day in class, take note of any changes
that you observe.
Measure the responding variable
• Draw a data table for recording radish plant
Growth (mm) in Light
Growth (mm) in Dark
Writing an experiment
Short description of procedure
Identify control and experimental groups.
Name the manipulated, responding
• Identify five constants