General Principles of Research Chapters 1 and 2 Next time: Chapter 3

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General Principles of Research (Chapters 1 and
2)Next time Chapter 3
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www.psych.ufl.edu/smiller
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General Principles of Research (Chapters 1 and
2)Next time Chapter 3
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The text suggests that research in developmental
psychology speaks to many everyday, real-world
issues of personal, social, or political
importance. Spend a week or so thinking about
this claim whenever you read the newspaper or
listen to the news. For how many of the topics
that you encounter in the news might an
understanding of principles of developmental
psychology be in some way valuable?One way to
gain a quick impression of the topics of current
interest within a field of study is by scanning
recent issues of some of the fields major
research journals. This is also a good way to get
ideas for your own research. Select at least
three of the journals listed in Table 1-2 and
locate their most recent volumes either at your
library or, if they are available electronically,
on-line (note that a volume, which typically
spans an entire year, includes several separate
issues). Read the titles of each of the articles,
and for any that you find intriguing, read the
abstract (which provides a brief summary of the
article) as well. Select two topics in
developmental psychology that especially interest
you, and conduct a PsycInfo search for each.
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Independent VariableDependent Variable
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Independent variable Variable that the
researcher controls through manipulation or
selection in order to examine effects on the
dependent variable
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Subject (Classificatory) Variable
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Dependent variable Variable that the
researcher measures in response to variations in
the independent variable
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Independent VariableLevels
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Independent VariableLevelsFactors
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Independent VariableLevelsFactorsFactorial
Design
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2 X 2
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2 X 22 X 3
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2 X 22 X 32 X 2 X 2
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Correlational research Form of research in
which there is no control of an independent
variable but rather examination of possible
relations between two or more measured dependent
variables
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Validity
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Validity

• Internal

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Internal validity Accuracy of conclusions
concerning cause-and-effect relations between the
variables of a study
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Threats to ValidityTable 2.5 (page 27)
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Validity

• Internal
• External

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External validity Accuracy with which the
results of research can be generalized
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Validity

• Internal
• External
• Construct

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Construct validity Accuracy of the theoretical
interpretation of the results of research
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Experimental Control
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Experimental Control

• Over the independent variable

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Experimental Control

• Over the independent variable
• Over other potentially important factors

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Confounding Unintended conjunction of two
potentially important variables
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Experimental Control

• Over the independent variable
• Over other potentially important factors

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Experimental Control

• Over the independent variable
• Over other potentially important factors
• Over participants

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Random sampling Procedure for selection of
research participants in which each member of the
target population has an equal chance of being
selected
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Convenience sampling Procedure for selection of
research participants in which selection is based
largely on availability or cooperation
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Random SamplingConvenience SamplingStratified
SamplingOversampling
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Random assignment Procedure for assigning
participants to experimental conditions in which
each participant has an equal chance of being
assigned to each condition
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Control over Participants

• Random assignment

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Control over Participants

• Random assignment
• Matching

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Control over Participants

• Random assignment
• Matching
• Within-subject testing

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Subject (Classificatory) Variables
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Subject (Classificatory) VariablesNo random
assignmentpossible selection bias
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Subject (Classificatory) VariablesNo random
assignmentpossible selection biasIndependent
variable too broadhard to interpret
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Outcomes (pp. 22-26)
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Main EffectsInteractions
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Main effect Research outcome in which an
independent variable has a direct effect on a
dependent variable that is independent of other
independent variables in the design
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No Hint Hint2 X X
Mean 2 5 X X
Mean 5 Mean NH Mean H
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No Hint Hint2 6 14
10 5 14 16 15
10 15
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No Hint Hint2 X X
Mean 2 5 X X
Mean 58 X X Mean 8 Mean NH
Mean H
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No Hint Hint2 6 14
10 5 14 16 158 18
20 19
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No Hint Hint2 6 14
10 5 14 16 158 14
16 15
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Interaction Research outcome in which the
effect that one independent variable has on the
dependent variable varies across the levels of
another independent variable
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No Hint Hint2 6 14
10 5 14 16 15
10 15
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Young
Old
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No Hint Hint2 6
14 10 5 24 24
24 15 19
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Ceiling Effect Performance on a dependent
measure that is at or close to the maximum value
possible
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Floor Effect Performance on a dependent measure
that is at or close to the minimum value
possible
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Immediate DelayedTrained 7.50
4.75 No training .50
.40
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Label Boy Girl NeutralBoys
Girls
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Label Boy Girl NeutralBoys
- Girls -
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Label Congruent Incongruent Boys
- Girls -