Which of the following types of bias can be reduced by allowing equal interview time -

Ans. is 'd' i.e., Interviewer bias Interviewer's bias o This type of bias may occurs when the interviewer knows the hypothesis and also knows who the cases are. o This prior information may lead him to question the cases more throughly than the controls regarding a postive history of the suspected causal factor. o This bias can therefore be reduced by allowing equal time to interview both cases and controls. o This bias can be eleminated by double blinding. Slection bias o This type of bias may occur when the cases and controls selected for the study group are not representative of the cases and controls in the general population. o This type of bias can be best controlled by its prevention i.e., by proper selection of a representative study group. Recall bias (Memory bias) : o This type of bias may occur when cases and controls are asked to recall ceain events, and subjects in one group are more likely to remember the event than those in the other group. o For example people take aspirin commonly and for many reasons, but patients diagnosed as having peptic ulcer disease may recall the ingestion of aspirin in greater accuracy than those without G I problems. Also patients who have had an MI are more likely to recall and remember ceain habits (like eating habit) with greater accuracy than those who have not had an MI.