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Research Methods in Psychology (Pp 84-104)


Research Methods in Psychology (Pp 84-104) – PowerPoint PPT presentation

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Title: Research Methods in Psychology (Pp 84-104)

Research Methods in Psychology(Pp 84-104)
IB Internal Assessment
  • The IB Psychology Guide states that SL
  • students are required to replicate a simple
  • experiment HL students may replicate an
  • existing study or conduct a modification of
  • an existing study.

Principles of Experimental Design
Overview of the Scientific Method
Literature Review
  • When writing your (IA) experimental report,
  • you will need to include
  • One relevant theory
  • 2-3 research studies (where one is explained in
    more detail than the others)

Experimental Variables
  • Independent Variable (IV)
  • is the variable being manipulated and controlled
    by the experimenter so that the effect can be
    measured. (Cause)
  • Dependent Variable (DV)
  • is the behavior to be measured that is
    dependent on the independent variable.

Research Groups
  • Experimental Group
  • Group of subjects exposed to the independent
  • Control Group
  • Subjects not exposed to some or all of the
    independent variable used to compare with the
    experimental group.

  • Research Hypothesis (Haµ gt 100)
  • Is a clear, concise prediction of what is
    expected to be demonstrated in the experiment.
  • Null Hypothesis (Hoµ 100)
  • States that no significant difference is
    expected to be found any results are simply due
    to some random variable or to chance.

Types of Experimental Hypothesis
  • One-tailed or Directional (gt or lt) Hypothesis
  • Predicts the direct effect of the Independent
    Variable has on the Dependent Variable. For
    example an authority figure observing a
    practiced behavior will reduce performance.
  • Two-tailed or Nondirectional (?) Hypothesis
  • Predicts that the Independent Variable will have
    an effect (of some sort) on the Dependent
    Variable, but the direction is not specified. For
    example an authority figure observing a
    practiced behavior will have an affect on

Experimental Validity
External Validity To what degree the results of
an experiment can be generalized to the
population and to what extent it represents a
real life situation. Internal Validity
Refers to whether the manipulated change in the
independent variable caused the change in the
dependent variable or whether something else
caused the change within an experiment. Internal
validity concerns come from random errors or
systematic errors.
  • The use of two or more methods of data collection
    in the study of some aspect of human behavior
    (Cohen et al, 2000)
  • Method triangulation
  • Time triangulation (cross-sectional,
  • Observer triangulation
  • Theory triangulation
  • Space triangulation
  • Combined levels of triangulation

Systematic and Random Errors
  • Systematic errors are made by the researcher (and
    should be controlled if possible)
  • Random errors are characteristics subjects bring
    with them to the study

Types of Systematic and Random Errors(Goodwin,
1998 Schumacher and McMillan, 1984)
  • History (RE)
  • Selection (SE)
  • Mortality (SE or RE)
  • Maturation (SE or RE)
  • Diffusion of Treatment (SE)
  • Response Style (SE)
  • Order Effect (SE)
  • Hawthorne Effect (RE or SE)
  • Experimenter Bias (SE)
  • Instrumentation (SE)
  • Constancy of Condition (SE)
  • Testing and Progressive Errors (SE)

Types of Experimental Design
  • Independent Samples (Between Group Designs) Some
    subjects are only exposed to part of the
    independent variable. Utilizes control groups.
  • Repeated Measures (Within Group Designs) All
    subjects are exposed to all parts of the
    independent variable
  • Matched Pairs Same kinds of subjects are assigned
    to each level of the independent variable.

Independent Samples/Between Groups
Recruit a group of participants
Divide them into two random groups
Group 1 Group 2
This group does the experimental task with the IV
set for condition 2
This group does the experimental task with the IV
set for condition 1
Measure the DV for each group
(No Transcript)
Independent Samples/Between Groups
  • What sort of problems are likely to arise from
    using two different groups of people?

Problem The natural variation between the
individuals (participant variables) in each
group may affect the DV measurements, making it
look as if the IV has had an effect when it
actually hasnt
Control After the subjects have been recruited,
they should be randomly assigned to their groups.
This should ensure the groups are similar, on
Repeated Measures/Within Groups
Recruit a group of participants
Condition 1 Condition 2 (Memorize
words (Memorize words without
music) with music)
The group does the experimental task with the IV
set for condition 1
The group repeats the experimental task with the
IV set for condition 2
Repeated Measures/Within Groups
  • What sort of problems are likely to arise from
    using the same group of people twice?

Problem Doing both conditions may (1) give
Subjects practice on the task (2) make them
bored or tired (3) allow them to work out the
aim of the study, all of which might affect the
DV measurement. (4) Reuse of stimuli is not
Control Divide the Subjects into two groups.
Half does condition A first, then condition B.
The rest do condition B then condition A. DV
measurements for the conditions A and B are then
compared (counterbalancing).
Matched Pairs
Recruit a group of participants
Find out what sorts of people you have in the
Recruit another group that matches them one for
Treat the experiment as independent measures
Condition 1 Condition 2
Matched Pairs
  • What sort of problems are likely to arise from
    using matched pairs of PPs?

Control Members of each pair should be randomly
assigned to conditions. However, this does not
solve all these problems.
Problem Several problems (1) time consuming
(2) an exact match is rarely possible (3) if one
PP drops out you lose 2 PPs data.
Choosing Participants
  • Determine your target population and then choose
    participants with the same characteristics as the
    population through
  • Simple random sampling
  • Stratified random sampling
  • Opportunity sampling

Random Allocation
Regardless of how samples are obtained, always
use random allocation to assign participants to
the groups or conditions.
Ways to Collect Data(Based on Type of Data to
  • Develop a task for subjects to complete
  • Observation grid
  • Questionnaire (see pp 101-104)
  • Always pilot your materials on a group
    similar to your participants before you run your

  • All procedures used must be clear and precise so
    others could replicate the experiment
  • Include any control features applied to your
    experiment that the design itself does not
  • Integrate how you met ethical requirements
    throughout the procedures

Experimental Ethics
  • APA requirements first do no harm
  • Informed Consent
  • IB Ethical Guidelines

Informed Consent(APA, 2002)
  • Purpose of study
  • Everything the participant is required to do
  • Potential risks and benefits from participation
  • Any situation where participants might be
    identified or quoted
  • Voluntary participation
  • How the data will be used
  • How to contact someone to find out the results of
    the study
  • Permission from parents for minors (under 16)

IB Ethical Guidelines
  • Handout
  • Signature sheet

The End