Experimental design Flashcards
Independent variable
Manipulated by the experimenter
Dependent variable
Measured by the experimenter (variable of interest)
Confounding variables
Controlled by the experimenter so their effect is minimised or removed
Cause false false results
Often confounding variables alter systematically with the IV and so the experimenter is not sure whether the changes in DV are due to confounding variables or IV
Ecological validity
How realistic a design is
Independent groups design - randomised controlled trial
Subjects divided into groups by strict randomisation
Check that the 2 groups don’t significantly differ nu chance in things such as age
Independent groups - pre existing groups
E.g elite vs novice
Matched pairs design - pre existing groups
E.g each participant in a group of adolescents with hyper mobility
Repeated measures design
Same subjects are tested under each conditions
Combination of multiple groups and multiple conditions.
E.g notice expert differences in the effect of anxiety on penalty accuracy
Quasi randomisation
E.g first participant through the door does A first, next participant does B
Hawthorne effect (threat to validity caused by participants knowing which group they are in)
Experimental group perform better as they know they are being tested
John Henry effect (threat to validity caused by participants knowing which group they are in)
Control group tries to be better and succeeds
Control group tries to outperform experimental group and succeeds
Placebo
Has all the characteristics of the manipulation apart form the 1 thing being investigated
Selection bias
results can’t be generalised
Assignment bias
Biased results affect scores award by experimenter
