experimental designs

independent group designs

separate groups of pp for each condition

strength for idependent group designs

• no order effects

• pp only do one task -wont benefit from practice

• increases validity of findngs

weakness for independent group designs

• diff pp in each group

• participant variables act as ev

• reduces validity of results

explain how allocation to conditions can help deal with participant variables

using random way to allocate pp into each conditions (systematic sampling)

repeated measures desings

all pp take part in all conditions

strength of repeated measures design

• no participant variables

• each pp compared against themselves

• increases findings validity

weakness of repeated measures designs

• order effects

• order they do tasks make difference

• decreases validity

explain how counterbalancing can deal with order effects

half pp complete conditions in one order other half complete in other order

matched pair designs

• pp paired on relevant variables

• pp than matched & one member from each pair goes in each group

strength of matched pair designs

• fewer pp variables

• matched on variable which is important for experiment

• increases validity

weakness of matched pair designs

• takes time matching pairs

• doesnt control all pp variables

• not worth it , decreases validity