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. (Effect)

Research Groups

Experimental Group Group of subjects exposed to the independent variable

Control Group Subjects not exposed to some or all of the independent variable; used to compare with the experimental group.

Hypotheses

Research Hypothesis (Ha:μ > 100)

Is a clear, concise prediction of what is expected to be demonstrated in the experiment.

Null Hypothesis (Ho:μ = 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 (> or <) 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 performance.

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.

Triangulation

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,

longitudinal) 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

This group does the experimental task with the

IV set for condition 1

This group does the experimental task with the

IV set for condition 2

Measure the DV for each group

Compare the results for the two groups

Group 1 Group 2

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 hasn’t

Control:After the subjects have been recruited, they should be randomly assigned to their groups. This should ensure the groups are similar, on average.

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

Compare the before/after results for the two conditions

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 possible.

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 PairsRecruit a group of

participants

Find out what sorts of people you have in the

group

Recruit another group that

matches them one for one

Condition 1 Condition 2

Compare the differences between the matched pairs

Treat the experiment as independent

measures

Matched Pairs

What sort of problems are likely to arise from using matched pairs of PPs?

Problem:Several problems: (1) time consuming; (2) an exact match is rarely possible; (3) if one PP drops out you lose 2 PPs’ data.

Control:Members of each pair should be randomly assigned to conditions. However, this does not solve all these problems.

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 Collect)

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 experiment

Procedures

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 control

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