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Repeated Measures: P's take part in every condition
being tested. Good for participant variables and fewer p's
needed. BUT order effects may occur (boredom, fatigue,
practice) and p's may guess the aim.
· Independent groups: P's take part in only one
condition, and their performance are compared. Avoids
issues that occur with repeated design but needs more p'
s. No control of participant variables but this can be
overcome by random allocation.
· Matched pairs: 2 groups of p's matched on key
participant variables. Avoids order effects and
particularly controls participant variables but matching is
· Counterbalancing can be used to avoid order effects by
ensuring each condition is tested first or second in equal
amounts. ABBA…read more

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Control refers to the extent to which any variable is held constant or
regulated by a researcher. The IV is controlled to observe its effect.
Extraneous variables are controlled so any effect can be attributed
to the IV, for example:
· Participant Variables: age, intelligence, motivation etc. may explain
why p's' in one group did better
· Situational Variables: time of the day, temperature, noise etc. may
also explain group differences
· Experimenter effects: unwittingly communicates info to p's which
may give them a clue as to how to behave
· Demand Characteristics: trigger a predictable response
Methods of control include:
· Single Blind technique: P's don't know true aim of the study
· Double blind technique: Investigators & P's don't know true aims…read more

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An experiment conducted in a specially-designed
environment where variables can be easily controlled
· Can draw casual conclusions
· Extraneous variables minimised
· Easily replicated ­ link to reliability
· High levels of control
· Tends to lack mundane realism
· Experimenter and participant effects
· Low ecological validity…read more

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An experiment conducted in p's own environment. P's
often unaware they are involved in an experiment.
· Can draw casual conclusion
· Higher ecological validity
· Avoids p effects if they are unaware
· Less control
· Demand characteristics may effect behaviour
· Possible ethical issues…read more

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A quasi-experiment that takes advantage of the fact that a
variable of interest (the IV) occurs naturally, so we can
observe the effects on the DV.
· Allows research where the IV cant be manipulates for
ethical/practical reasons
· Enables psychologists to study `real' problems
· Can't show casual relationship
· May be extraneous variables
· Experimenter and participant effects…read more


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