1.4 - experiments

what are the types of experimental designs?

independent measures, repeated measures and matched pairs

what is the strength of independent measures design?

no order effects as they only experience one condition - increases internal validity

what is the weakness of independent measures design?

low levels of control over individual differences (someone may have more age/ability) - reduces internal validity

what is an experimental hypotheses?

indicates the differences that will be found ‘there will be a significant increases/decrease..’

what is a two-tailed hypothesis?

states that there will be a difference but doesn’t state the direction ‘there will be a significant difference…’

what is a null hypothesis?

‘there will be no significant difference…’

what are the types of experimental methods?

lab, field and quasi

what are lab experiments?

IV is manipulated in order to measure its effect on the DV (behaviour). EVs highly controlled and held constant 

what are field experiments?

experimenter manipulates the IV and measures the effect/change on the DV. takes place in a natural environment 

what are examples of where a field experiment would take place?

house, place of work/study

what is a quasi experiment?

IV is naturally occurring and cannot be manipulated . DV is then measured. takes place in a lab/field setting 

what are the 2 types of variables other than IV and DV?

extraneous and confounding (EV/CV)

what are extraneous variables?

other things that could affect the research - should be controlled if possible

what are confounding variables?

reduce the validity and accuracy of findings because they ‘confuse’ the results 

what are the types of EVs?

environmental (temperature, noise, lighting)
participant characteristics (sex, age, individual differences)
experimenter characteristics (appearance, sex, age)

what are the strengths of field experiments?

carried out in real life settings resulting in high ecological validity - reflects real life behaviour
participants are in natural environments (less demand characteristics) which increases validity - increases accuracy

what is the weakness of field experiments?

natural environment leads to low levels of control over EVs which decreases validity as other variables than the IV can affect behaviour (DV) - reduces accuracy

what is the strength of quasi experiments?

ale to investigate behaviours which would otherwise be impossible or impractical which doesn’t breach ethical guidelines - doesn’t damage the reputation of psychology, future funding or recruitment of participants

what is the weakness of quasi experiments?

lack of control over individual differences which decreases validity - reduces accuracy

what is the strength of IMD?

no order effects as they only experience one condition - increases internal validity

what is the weakness of IMD?

low levels of control over individual differences (someone may have more age/ability) - reduces internal validity

what is the strength of matched pairs?

high levels of control over individual differences as participants matched on relevant criteria - increases internal validity

what is the weakness of matched pairs?

time consuming if at all possible to match participants on relevant criteria - could be a waste of funding as it could be costly to match people

what is the strength of RMD?

high levels of control over individual differences because each person is being compared to themselves - increases internal validity

what is the weakness of RMD?

prone to order effects as they have experienced both conditions and can become better practiced/perform worse due to boredom and tiredness - reduces internal validity