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Lecture 9

PSY 240 Lecture Notes - Lecture 9: Statistical Power, Null Hypothesis, Random AssignmentPremium

2 pages60 viewsFall 2017

Course Code
PSY 240
Nathan Singley

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Psychology 240 (Nathan Singley)
Yellow = Important Concepts
Chapter 6: The Experiment
Let’s Define Our Variables
Independent variable (what we manipulate): number of hours of study
Dependent variable (what we measure): GPA
Operationalizing the variables:
o Independent variable
Low/Med/High # hours of study in controlled environment
o Dependent variable
GPA reported by school administration at point of graduation
o Cluster sample
o Max possible GPA of 4.0
o N = 300
o Students have now graduated
Subject assignment:
o How will we assign our subjects to the levels/conditions of our
factors/independent variables?
o Random assignment to low/med/high
True experiment uses random assignment
o Quasi-experiment is the same thing, but w/o random assignment
o Non-experiment is used for the collection of information (survey)
Materials, methods, and procedures
o How will we physically carry out our experiment?
Cluster sample freshmen, randomly assign to study groups 1, 2, or 3,
corresponding to low/med/high number of hours of study per week in a
controlled environment
Collect dependent variable via transcript request to graduating institution
Do we have the makings of a true experiment?
o Random sampling
o Control of the environment and variables
o Operationalized definitions
Between-groups or within-groups?
o Will we be using repeated-measures or independent measures?
Are we comparing subjects with themselves or are we comparing one
group with another group?
Will There Be Order Effects?
Do we need to randomize or counterbalance the order of our conditions?
o Randomization is literally random
o Counterbalancing has a specific order
Can we fully counterbalance or do we need to utilize Latin Squares?
o Best to make the experiment as simple as possible; eliminate too many conditions
What are Potential Confounds?
Studying outside of the allotted time
o Tell them they’re not allowed to
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