Scientific Method Review

Scientific Method Vocabulary
Robert Strawn
Stating the problem
• What do you want to know?
What causes leaves to change color during
the fall?
• State the problem as a question.
Example: Why do leaves change colors in the
fall ?
• An hypothesis is a limited statement regarding
cause and effect in specific situations; it also
refers to our state of knowledge before
experimental work has been performed and
perhaps even before new phenomena have
been predicted.
• A hypothesis is a tentative explanation about the
natural world; a concept that is not yet verified
but that if true would explain certain facts or
• Scientist use an experiment to look for
cause and effect relationships in nature.
• They design an experiment so that
changes to one Variable (any factor, trait
or condition that exist in differing amounts
or types), causes something else (another
variable) to vary in a predictable way.
• Experiments test hypothesis.
Independent variable
• Sometimes called the manipulated
• The part of the experiment that is
manipulated or changed by scientists or
persons performing the experiment.
• Independent Variable = what you are
testing or what you are in control of or
what you manipulate
Dependent Variable
• Some times called the responding
• The part of the experiment that is being
affected by the independent variable.
• Changes in the Dependent variable are
caused by a change in the independent
• Dependent Variable=what you are
Controls or Controlled
• Quantities that a scientist wants to remain
• A part of the experiment that is not being tested
and is used for comparison of the experimental
• A control group should be used when
conducting an experiment. This group receives
the same attention as the test groups, however,
it will not be influenced by the variable the other
groups are testing.
• Controlled variables are quantities that a
scientist wants to remain constant, and he
must observe them as carefully as the
dependent variables.
Other Important Terms
Sample: a chosen population to represent a
scientific study.
- Example: AHS students, Males, Hispanics,
- Use common sense when choosing a sample
-Random sampling- Each member of the
population has an equal chance of being
selected. (best sample)
Experimental group: group(s) subjected to the
independent variable
Control group: group not subjected to the
independent variable, used as measuring
• reproducibility: producing the same result
consistently to verify result. It is therefore
important to describe your experimental design
in enough detail for others to perform the same
• A successful Experiment is repeatable.
– By anyone.
– Examples:
– Cold Fusion (1989)
– Ecstasy (Science, 2003)
• Assumptions: factors thought to be
true for the investigation but have not
been verified or controlled
– Commonly accepted information
– Thought to be held constant but not controlled
– Factors beyond the investigators control
because of technical or time considerations
• Incorrect assumptions invalidate an
• Statistics – using mathematics to organize,
summarize, and interpret numerical data
• Mean: arithmetic average of scores
• Variability = how much scores vary from
each other and from the mean