Which of the following can be eliminated by double blinding: March 2009

Ans. C: Interviewer's bias Park's PSM,21st ed., p-70 states: Interviewer's bias: Bias may also occur when the interviewers knows the hypothesis and also knows who the cases are. This type of bias can be eliminated by double blinding. Interviewer's bias may occur when the interviewer knows the hypothesis and also knows who the cases are. This prior information may lead to question the cases more thoroughly than controls regarding a positive history of the suspected casual factor. This type of bias can be eliminated by double-blinding. In a double-blind experiment, neither the individuals nor the researchers know who belongs to the control group and the experimental group. Only after all the data have been recorded (and in some cases, analyzed) do the researchers learn which individuals are which. Performing an experiment in double-blind fashion is a way to lessen the influence of the prejudices and unintentional physical cues on the results (the placebo effect, observer bias, and experimenter's bias). Random assignment of the subject to the experimental or control group is a critical pa of double-blind research design. The key that identifies the subjects and which group they belonged to is kept by a third pay and not given to the researchers until the study is over. Double-blind methods can be applied to any experimental situation where there is the possibility that the results will be affected by conscious or unconscious bias on the pa of the experimenter. Computer-controlled experiments are sometimes also erroneously referred to as double-blind experiments, since software may not cause the type of direct bias between researcher and subject.