psyc 321_06 threats to validity and control
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Transcript of psyc 321_06 threats to validity and control
04/10/2023 1
Developmental Research MethodsTopic 5: Testing Hypotheses
CEDP321 Ryan Sain, Ph.D.
VariationRemember, we are interested in
two types of varaiationSystematic and unsystematic
(chance)There are two sources of
systematic variance◦Ones due to the IV◦Ones due to confounds
Types of Error
The Null Hypothesis Is …..
True False
Based on the Test, We
either…
Fail to Reject the Null
RESEARCH OBJECTIVE
TYPE II ERROR
β
Reject the NullTYPE I ERROR
α
RESEARCH OBJECTIVE
04/10/2023 CEDP 596-04 Ryan Sain, Ph.D.
Threats to ValidityInternal:
◦History◦Maturation◦Instrumentation◦Selection◦Testing effects
Pretest sensitization
◦Regression toward the mean
◦Mortality
04/10/2023 CEDP 596-04 Ryan Sain, Ph.D.
More Threats
Reactance◦To experiment –
Hawthorne◦Expectancy Effect◦To testing (sensitized)
Multiple treatment◦Cannot control for prior
treatments
04/10/2023 CEDP 596-04 Ryan Sain, Ph.D.
Even more threatsSubject –
Experimenter Effects◦Hypothesis guessing◦Diffusion of treatment◦Good subject effect◦Evaluation
apprehension◦Obedience
Demand Characteristics◦Acting out the role of
subject
04/10/2023 CEDP 596-04 Ryan Sain, Ph.D.
Control
Controlling for confounds◦ Constancy of
conditions THOUSANDS of
designs Experimental Quasi-experimental Varying levels of
internal validity Do what you can
04/10/2023 CEDP 596-04 Ryan Sain, Ph.D.
Controlling for threats
Random assignment
Pilot studies◦ Quasi-control
subjectsBlindingDistracter
itemsStandardizin
g
04/10/2023 CEDP 596-04 Ryan Sain, Ph.D.
Creditswww.sxc.hu
◦Padlocks and faces – emospada◦Steering Nature – johnnyberg◦Spices – pape2000