Single-blind and double-blind procedures

Single-blind procedure

The researchers do not tell the Ps if they are being given a test treatment or a control treatment. This is done to ensure that Ps do not bias the results by acting in the ways they think they should act — avoids demand characteristics.

Double-blind procedure

Neither the Ps nor the experimenter knows who is receiving a particular treatment — prevents bias in researcher results.

Double blind

Useful for preventing bias due to demand characteristics or the placebo effect. Gives a way to reduce the investigator effects as the investigator is unable to unconsciously give Ps clues as to which condition they are in.

Control group / conditions

Sets a baseline where results from the experimental condition can be compared to results from this one. If there is a significantly greater change in the experimental groups compared to the control than the researcher is able to conclude that the cause and effect was the IV.