WBR0742

Author	[[PageAuthor::Yazan Daaboul, M.D. (Reviewed by Serge Korjian)]]
Exam Type	ExamType::USMLE Step 1
Main Category	MainCategory::Biostatistics/Epidemiology
Sub Category	SubCategory::Gastrointestinal
Prompt	[[Prompt::A researcher is studying the optimal dose of ranitidine required for relief of gastroesophageal reflux disease symptoms (GERD). He enrolls 240 patients known to have GERD and who complain of have similar symptoms. The patients receive oral ranitidine in 50 mg increments every 24 hours until they reach the dose that provides them with symptomatic relief. Following data collection, the researcher demonstrates his findings on the graph shown below. Based on his findings, which of the following statements regarding the mean, median, and mode is correct? ]]
Answer A	[[AnswerA::Median > Mode > Mean]]
Answer A Explanation	AnswerAExp::This is not the relationship in positively skewed graphs.
Answer B	[[AnswerB::Mode > Median > Mean]]
Answer B Explanation	AnswerBExp::This would be a correct answer in negatively skewed graphs.
Answer C	[[AnswerC::Mean > Median > Mode]]
Answer C Explanation	AnswerCExp::This is the correct relationship between mean, median, and mode in positively skewed graphs.
Answer D	[[AnswerD::Mean > Mode > Median]]
Answer D Explanation	AnswerDExp::This is not the relationship in positively skewed graphs.
Answer E	[[AnswerE::Mode > Mean > Median]]
Answer E Explanation	AnswerEExp::This is not the relationship in positively skewed graphs.
Right Answer	RightAnswer::C
Explanation	[[Explanation::Based on the graph above, the distribution of the researcher's findings show a positively skewed graph because the tail of the graph is towards the positive side. In such graphs, the relationship of the mean, median, and mode are always as follows: mean > median > mode. In contrast, a negatively skewed graph, where the tail is towards the more negative values, the relationship is always as follows: mode > median > mean. Notably, in both positively and negatively skewed graphs, the median is always in the middle. Graphs with normal distribution typically have mean = median = mode. Educational Objective: Positively skewed graphs, with the tail towards the more positive side, always have mean > median > mode. References: Chow S, Liu J. Design and Analysis of Clinical Trials, Concepts and Methodologies. John Wiley & Sons; 2013.]]
Approved	Approved::Yes
Keyword	WBRKeyword::Median, WBRKeyword::Mode, WBRKeyword::Mean, WBRKeyword::Skew, WBRKeyword::Skewed, WBRKeyword::Normal distribution
Linked Question	Linked::
Order in Linked Questions	LinkedOrder::