WBR0741

Author	[[PageAuthor::Yazan Daaboul, M.D. (Reviewed by Yazan Daaboul, M.D.)]]
Exam Type	ExamType::USMLE Step 1
Main Category	MainCategory::Biostatistics/Epidemiology
Sub Category	SubCategory::Cardiology
Prompt	[[Prompt::A cardiologist who interprets echocardiograms notes his observations before he reads the relevant clinical history of the patient. After documenting his findings, he retrieves the patient's chart and compares his findings to the patient's clinical data. When asked by his student, the cardiologist replies that this technique is designed to prevent bias. Which type of bias is this technique most likely preventing?]]
Answer A	AnswerA::Procedure bias
Answer A Explanation	AnswerAExp::An example of procedure bias is when subjects of two arms of a study experience a different course during the study or are treated differently.
Answer B	AnswerB::Lead-time bias
Answer B Explanation	AnswerBExp::An example of lead-time bias is when early detection is misinterpreted as increased survival.
Answer C	AnswerC::Recall bias
Answer C Explanation	AnswerCExp::An example of recall bias is when a person experiencing a disease might know more of the disease than subjects who do not experience the disease.
Answer D	AnswerD::Selection bias
Answer D Explanation	AnswerDExp::An example of selection bias is when subjects are selected in a non-random fashion.
Answer E	AnswerE::Observer bias
Answer E Explanation	AnswerEExp::An example of observer bias is when the researcher is aware beforehand of what to expect and is unconsciously influenced by his knowledge.
Right Answer	RightAnswer::E
Explanation	[[Explanation::Using the blinded technique, the cardiologist is reducing observer bias (also known as experimenter's bias or researcher's bias). Observer bias is defined as a bias due to the presence of a pre-existing knowledge among the physician/researcher that unconsciously alters results to change the study's outcome. Observer bias is also seen in clinical trials when an investigator knows beforehand which group of subjects is receiving a specific medication; this knowledge might unconsciously influence investigator to alter his findings to match the study's expectations. In this vignette, the cardiologist is documenting his findings blindly to reduce the observer-expectancy effect induced by observer bias. Educational Objective: An example of observer bias is when the researcher is aware beforehand of what to expect and is unconsciously influenced by his knowledge. Blind experimentation reduces observer bias. References: First Aid 2014 page 55]]
Approved	Approved::Yes
Keyword	WBRKeyword::Observer, WBRKeyword::Bias, WBRKeyword::Blind, WBRKeyword::Experiment, WBRKeyword::Technique, WBRKeyword::Observer-expectancy bias, WBRKeyword::Observer expectancy bias, WBRKeyword::Observer bias, WBRKeyword::Experimenter bias, WBRKeyword::Experimenter's bias, WBRKeyword::Researcher bias, WBRKeyword::Researcher's bias, WBRKeyword::Influence
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