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Lecture 2

# SOCPSY 1Z03 Lecture Notes - Lecture 2: Internal Validity, Random Assignment, Dependent And Independent Variables

Department
Social Psychology
Course Code
SOCPSY 1Z03
Professor
glav
Lecture
2

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Research Methods
Causal relationship between variables.
Independent variable has an EFFECT (x) on the dependent variable (y)
Extraneous variables (z) variable that may effect (x) or (y)
Causality: temporal order, co-variation (association or correlation) but correlation
=/= causation
Spuriousness: when an apparently causal relationship between 2 variables
2 types of validity: 1. Internal validity: when a causal relationship is properly
demonstrated. 2. External validity: when a causal relationship can be generalized
to a broader pop. Or setting
Two features to help establish causality: manipulation of IV and random
assignment to levels (ex. Control group vs experiment group) of the IV
Other experimental terms: treatment vs control group, field vs laboratory
experiments
More challenges to experimental designs:
1. Experimenter effect: the experimenter wants to see certain results so they
influence the subjects and affect performance. Solution: Double-blind experiment:
neither the experimenter nor the subjects know who is assigned to which group.
Experiments: strengths and weaknesses:
STRENGTHS: strong internal validity, artificiality, replication
WEAKNESSES: unrealistic lab setting (threat to internal validity), weaker
external validity (generalizing to broader groups can be difficult), sometimes
unethical
SURVEY METHODS
Procedure for collecting info by asking members of a pop. To answer a set of
questions.
Can be used for descriptive and explanatory studies
Most often, people are the unit of analysis
The person is called a RESPONDENT (a person who provides data for analysis
by responding to a survey questionnaire)
Surveys are excellent tools for measuring the attitudes and orientations of a large
pop.
Strengths: cheaper, easier to generalize to broader pop. (strong external validity),
can test mean hypothesis in a single survey
Weakness: Harder to establish internal validity (less control over IV), self-reports
bias
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