The Science of Psychology
The Scientific Method and
Research Design
Experimental Research
 With experimental research, one can determine
cause and effect among variables.
 Experiments allow researchers to manipulate or
control one variable to observe the effect of that
manipulation on another variable, while holding all
other variables constant.
More on Experimental Research
 There are several terms you need to
memorize regarding experimental
research.
Hypothesis
 A statement about the relationship between two
or more variables
 Must be testable
Key Terms - Variables
 Variables- Factors that change in an
experiment
 Independent Variable (IV)- The factor that the
experimenter manipulates or changes
 Dependent Variable (DV)- The factor being
measured
 Extraneous or Confounding Variable- An undesirable
variable that influences the relationship between the
IV and DV, though it is not the variable of interest.
 These variables are undesirable because they ADD
ERROR to an experiment. A major goal in research
design is to decrease or control the influence of
extraneous variables as much as possible.
 Ex post facto – Research in which we choose subjects
based on a pre-existing condition.
Key Terms – People Involved
 Subjects- Animals or humans used in your study
 Participants- Humans used in your study
 Confederate – Someone who is in on the experiment but
pretends to know nothing about it
 Population- The large group containing all potential
participants for your study (can be defined in many ways)
 Sample- Small subgroup of participants chosen from the
larger population
Key Terms – People Involved
 Experimental Group- The group that
experiences the IV; OR the group on
which the critical part of the
experiment is performed
 Control Group- The group that does
not experience the IV; OR the group
that does not participate in the
critical part of the experiment
Key Terms - Locations
 Lab setting- Gives the researcher
greater control over variables, but
may not be a perfect replication of
the real-world environment
 Field setting- Gives a more natural
look at the participants because they
are in their natural habitat, but the
researcher has less control
Key Terms – Control Measures
 Single-Blind: subject unaware of assignment
 Double-Blind: subject and experimenter
unaware of placement
 Randomization
 Random Sampling
 To randomly select participants from population
 Allows you to generalize results
 Random assignment
 To randomly divide participants into groups
 Either the _____________ or _____________ group