BHS 204-01
Methods in Behavioral
Sciences I
Nancy Alvarado, Ph.D.
What is an Experiment?
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A sample experiment – the Pepsi Challenge.
Start with a set of questions:
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Can people really tell the difference between
Pepsi and Coke?
How is preference for one or the other cola
related to being able to tell the difference?
Does it matter which order you drink the two
flavors in?
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Coke first vs Pepsi first
Finding Answers
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How do you answer the questions you’ve
come up with?
Experimental design for Pepsi Challenge:
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Get a group of people
Let them taste the two kinds of cola
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Half taste Pepsi first, half taste Coke first
Ask them questions:
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Which is Pepsi?
Which do you prefer?
Making Predictions
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A researcher generally has some idea about
how the experiment will turn out:
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Predictions come from theories, from
observations of real life behavior, and from the
experimenter’s own experience and beliefs.
State predictions in terms of the experiment:
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People will prefer Pepsi, people can tell which is
which, order will not make a difference.
Run the Experiment
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Collect data
Analyze the data:
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Descriptive statistics – summarize data
Inferential statistics – test your results against
what might have occurred by chance.
Use the data to test the predictions:
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How many people ID and prefer Pepsi vs Coke?
Did order of tasting affect the choices?
Present the Findings
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An experiment is wasted if its results are not
communicated to the public and to the
scientific community.
Vehicles for communicating:
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Conferences
Professional journals
Public – press releases, TV, radio, popular books
Questions Lead to More Questions
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Does it matter whether the Pepsi is tasted cold
or warm?
How do people identify it?
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Bubbles – amount of carbonation?
Sweetness – does Pepsi have more sugar?
Are factors beyond taste important to
preference?
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Brand loyalty, image (rebels drink Classic Coke)?
Terminology
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Subject or participant – a person who provides
information or data in a study.
Dependent variable – what is measured during
your study.
Independent variable – what is manipulated
during your study.
Condition – which group a person is assigned
to in the study.
What is an Experiment?
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A controlled situation in which the researcher
manipulates at least one variable in order to
observe the effect of that change on subject
behavior.
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There must be at least one independent variable
that is manipulated by the experimenter.
There must be at least one dependent variable that
is measured by the experimenter.
Experiments can tell you about causes.