Controls

General Strategies Single-Blind and Double-Blind Procedures		< back		11 of 25		next >

Bias can be introduced into studies by both the experimenter and the participant. Direct knowledge of the study hypothesis, the nature of the experimental manipulation, and group assignment can lead to subtle differences in the ways that experimenters and participants interact in the research setting. Restricting knowledge of the experiment through "blind" procedures can help to eliminate this bias.

	In a single-blind procedure, a laboratory assistant who does not know the study hypothesis administers the experimental manipulation. The laboratory assistant also does not know the experimental condition to which the participant was assigned. Having a naive intermediary between the experimenters who designed the study and the research participants prevents experimenter expectancies from influencing study results.