Variables and Controls
Variables and the Experimental MethodIndependent
VariableCaffeineTimeof day influencesDependent VariableNumber of
words recalledTea/CoffeeNoise
ExtraneousVariables
2 ConditionsIndependent VariableCaffeine influencesDependent
VariableNumber of words recalledTea/CoffeeNoise
ExtraneousVariablesConfoundingVariableTimeof dayPsychologists
try to control extraneous variables so that they dont become
confounding variables.This means experiments can show cause and
effect.Independent VariableCaffeineTimeof day influencesDependent
VariableNumber of words recalledTea/CoffeeNoise
These are controlsAll tested at 9 amNo caffeine drinks for 12
hours previouslyQuiet environment usedThere are 3 types of
variables to controlControls
Participant VariablesHeatTime of
dayIntelligenceAgePersonalityParticipant reactivityTone of
voiceDemand CharacteristicsOrder EffectsSituational VariablesBody
languageBiasExperimenter VariablesParticipant Variables
Individual DifferencesAge, gender, mood, background, ethnicity,
IQ, personality, memory, beliefs, past experiences.
Controls for Individual DifferencesSampleSample large and
randomly to gain representative samplesDesignUse Repeated Measures
or Matched PairsAllocationRandomly allocate to conditionsControls
for Situational Variables 1. Standardise keep everything the same
for each participant
Standardise ProcedureStandardise Instructions
Controls for Situational Variables 2. Counterbalance to reduce
effect of situational variables or order effects
Split the group in half
Group 1 do condition 1 > 2Group 2 do condition 2 > 1
This balances out any order effects. E.g. If you do better on
the 2nd test, 50% will do better in Condition 1 and 50% do better
in condition 2
Demand Characteristicsrefers to an experimental artefact where
participants form an interpretation of the experiment's purpose and
unconsciously change their behaviour accordinglyControls for Demand
CharacteristicsDistractor questionsLying about the aimThe
participant is unaware of which condition theyre inSingle
BlindDeceptionPlaceboDrugExperimenter VariablesThe experimenter
effect is a term used to describe subtle cues or signals from an
experimenter that affect the performance of participants in
studies.
The cues may be unconscious nonverbal cues, such as muscular
tension or gestures. They may be vocal cues, such as tone of
voice.Experimenter Variables
My beliefs about what Im studying can create bias. This could be
subconsciously (or consciously). This is experimenter bias.
Controls for Experimenter VariablesDoubleBlindNeither the
researcher or the participant knows which condition they are
inInter-rater reliabilityIndependent raters rate same behaviour as
researcher check for agreement
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