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

Standardised ProcedureStandardised 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 or consciously 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 agreementOperationalisation

just means making clear how you measure something.e.g. ppts who listen to music will have better memories than ppts who dont is a hypothesis. What would the operationalised version look like?ppts who listen to Abbas take a chance on me for 2 minutes will recall more words out of 20 from a word list than ppts who listen to silence for 2 minutes

IV the thing I Vary DV the thing I measure, the thing I get my Data VromThe second version is much more precise it has been operationalised!

And now to your science pack.