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overview of between (independent) subjects designs (3)
-typical experimental procedure
-each group contains different people
-comparisons are between different groups
overview of within subjects designs (2)
-independent variable represents more than one assessment of the same group, under different conditions
-other IVs may be
between
subjects (mixed design)
COre issues of within subjects designs (3)
-many research questions address contrasts
between
different states
within
one person.
-many studies address change over time
-practical efficiency of within Ss designs
*powerful contrasts within subjects; less within group variance
*studies that require rare or costly participants
Basic between-subjects design (4)
-clear experimental manipulation
*treatment given to only one group
-hypothesis tested via differences between groups
-
internal validity
groups must differ
only
on
IV
statistical power
requires larger number of subjects
Within subjects designs
-hypothesis
tested by
differences between conditions
within group
-
internal validity
: eliminate possible confound of group differences at baseline since there is only one group
-
statistical power
increased, requires fewer subjects
-
experimental manipulation
potentially less clear
-possible
carry-over effects
***efefcts of being in one experiment then going into anohter but carrying those effect over
Within subjects designs with
Counter balancing?
-internal validity
*eliminate confound of group differences at baseline
*lessens carry-over effects
-statistical power
design requires more subjects
whats counter balancing?
one group will be set for control while the other is experimental in the within subjects design to prevent carry-over effects. then they switch
Advantages of within subjects designs (3)
-participant assignment problems eliminated, since there is only one group
*no need for random assingment
*no problem wiht groups being equal at baseline
-can use a smaller n than between Subjects
*half as many participants
** very useful for rare or expensive participants
-more senstive to experimental effects; less within subject (error) variance
Disadvantages of within-subjects designs
-participant "burden"
*fatigue from multiple experimetns
*possibly drop out
-sequencing or order effects
*scores change if participants learn or get practice over different conditions
*participants get sensitized to experiment
*cure by counter-balncing order of condition takes about as many participants as
between group design
.
Brief problems on within subjects designs
-carryover effects
-maturation
-testing
Within subjects design are somewhat common in psychological research
-own control design create stonrg contrast for IV
-eliminate probems in creating experimental versus control group
Author
efrain12
ID
186155
Card Set
within subjects
Description
pp
Updated
2012-11-30T00:58:43Z
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