Experimental design – how Ps Experimental design – how Ps are allocated to each condition are allocated to each condition

of the IVof the IV

RRepeated measuresepeated measuresIIndependent measuresndependent measuresMMatched participantsatched participants

Independent MeasuresIndependent MeasuresRecruit a group of

participantsDivide them

into two

This group does the experimental task with the

IV set for condition 1

This group does the experimental task with the

IV set for condition 2

Measure the DV for each group

Compare the results for the two groups

Repeated MeasuresRepeated MeasuresRecruit a group of

participants

Condition 1 Condition 2

The group does the experimental task with the

IV set for condition 1

The group repeats the experimental task with the

IV set for condition 2

Compare the results for the two conditions

Matched ParticipantsMatched ParticipantsRecruit a group of

participants

Find out what sorts of people you have in the

group

Recruit another group that

matches them one for one

Condition 1 Condition 2

Compare the results for the matched pairs

Treat the experiment as independent

measures

Independent MeasuresIndependent Measures

AdvantagesAdvantages

No order effectsNo order effects

Fewer demand Fewer demand characteristicscharacteristics

Same materials can be Same materials can be used with each used with each conditioncondition

DisadvantagesDisadvantages

Participant variables – Participant variables – extraneous variable?extraneous variable?

More participants More participants requiredrequired

Repeated MeasuresRepeated Measures

AdvantagesAdvantages

Participant variables Participant variables are controlledare controlled

Fewer participants Fewer participants requiredrequired

DisadvantagesDisadvantages

Order effects (practice, Order effects (practice, boredom)boredom)

Demand Demand characteristicscharacteristics

Different materials Different materials must be used in each must be used in each conditioncondition

Matched ParticipantsMatched Participants

AdvantagesAdvantages

Participant variables Participant variables are controlledare controlled

No order effectsNo order effects

Fewer demand Fewer demand characteristicscharacteristics

Same materials can be Same materials can be usedused

DisadvantagesDisadvantages

Perfect matching is Perfect matching is not possiblenot possible

Time consuming to Time consuming to match Psmatch Ps

More participants More participants neededneeded

Match the key term to the Match the key term to the definitiondefinition

Key termKey term• Participant VariablesParticipant Variables

• Order effectsOrder effects

• CounterbalancingCounterbalancing

DefinitionDefinitionAn EV that occurs in a repeated An EV that occurs in a repeated measured design – Ps either get measured design – Ps either get bored or get better through bored or get better through practice so performance changespractice so performance changes

An experimental technique used to An experimental technique used to overcome order effects – half Ps overcome order effects – half Ps are tested in one condition first are tested in one condition first and half the other first, e.g. ABBAand half the other first, e.g. ABBA

A type of EV in which any A type of EV in which any characteristic of individual characteristic of individual participants may affect results (in participants may affect results (in independent measures design)independent measures design)