- confounding of variables: inadvertent simultaneous manipulation of
more than 1 variable. The results of an experiment involving confounded
variables permit no valid conclusions about cause and effect.
- counterbalancing: a systematic variation of conditions in an experiment
such as the order of presentation of stimuli, so that different participants
encounter them in different orders; prevents confounding of independent
variables with time-dependent processes such as habituation.
PERFORMING AN EXPERIMENT
- decide how to best conduct it (what participants, what instructions…etc)
Reliability of Measurements
- reliability: the repeatability of a measurement; the likelihood that if the
measurement was made again it would yield the same value.
- interrater reliability: the degree to which 2 or more independent
observers agree in their ratings of another organisms behaviour. (higher =
Selecting the Participants
- random assignment: procedure in which each participant has an equally
likely chance of being assigned to any of the conditions or groups of an
- researcher must continue to attend to the possibility of confounded
variables even after the experiment is under way.
- observation can change that which you observe
- if research participants figure out the researcher’s hypothesis, they will
sometimes behave as if the hypothesis is true (even if its not).
- single blind experiments:
- placebo: an inert substance that cannot be distinguished in
appearance from a real medication; used as a control substance in a single-
blind or double blind experiment.
- single blind study: an experiment in which the researcher but
not the participant knows the value of the independent variable.
- double blind experiments: