WBR0365: Difference between revisions

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|MainCategory=Biostatistics/ Epidemiology
|MainCategory=Biostatistics/ Epidemiology
|SubCategory=General Principles
|SubCategory=General Principles
|MainCategory=Biostatistics/ Epidemiology
|MainCategory=Biostatistics/ Epidemiology
|MainCategory=Biostatistics/ Epidemiology
|MainCategory=Biostatistics/ Epidemiology
|MainCategory=Biostatistics/ Epidemiology
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|MainCategory=Biostatistics/ Epidemiology
|MainCategory=Biostatistics/ Epidemiology
|SubCategory=General Principles
|SubCategory=General Principles
|Prompt=A research group is trying to study the effects of concentrated coffee bean extract . They design a double blinded study recruiting 150 subjects. Subjects are randomized in a blind fashion into 2 groups. One of the groups is given the active treatment and the other group is given placebo. At the end of the 3 month period, the research group wants to compare the body weight change (delta weight) after given the treatments. They want to compare the mean of the two different groups to determine if a statistical significance was achieved. Which of the following tests should the researchers use in order to compare the 2 groups?
|Prompt=A research group is trying to study the effects of a short course of concentrated coffee bean extract on weight loss in healthy volunteers. They design a randomized double-blinded controlled trial and recruit 154 subjects. Subjects are randomized in into 2 groups one receiving 3 daily doses of coffee bean extract and the other receiving 3 daily doses of a placebo. At the end of the 6 month period, the biostatistician wants to compares the mean change in body weight from baseline in the 2 groups. Which of the following tests should the biostatistician use in order to obtain a valid comparison?
|Explanation=The research group is trying to compare the mean value of the weight change between two groups, therefore it the test recommended is t-test. This statistical test allows to compare the means of two groups.
<br>
'''Educational Objective:''' T- test is used to check if a difference exists between the means of 2 groups.
|AnswerA=Chi-square
|AnswerA=Chi-square
|AnswerAExp=[[Chi-square test|Chi-square]] is a test which allows to determine a difference between 2 or more proportions or percentages of categorical outcomes.  
|AnswerAExp=[[Chi-square test|Chi-square]] is a test which allows to determine a difference between 2 or more proportions or percentages of categorical outcomes.
|AnswerB=ANOVA
|AnswerB=ANOVA
|AnswerBExp=[[ANOVA]] or analysis of variance allows to determine if a difference exists between the means of 3 or more groups. ANOVA (Analysis of Variance of 3 or more groups).
|AnswerBExp=[[ANOVA]] or analysis of variance allows to determine if a difference exists between the means of 3 or more groups. ANOVA (Analysis of Variance of 3 or more groups).
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|AnswerE=Power measure
|AnswerE=Power measure
|AnswerEExp=Power measure
|AnswerEExp=Power measure
|EducationalObjectives=T- test is used to check if a difference exists between the means of 2 groups.
|RightAnswer=C
|RightAnswer=C
|Approved=Yes
|Approved=Yes
}}
}}

Revision as of 20:41, 30 July 2014
Author [[PageAuthor::Gonzalo A. Romero, M.D. [1]]]
Exam Type ExamType::USMLE Step 1
Main Category MainCategory::Biostatistics/ Epidemiology
Sub Category SubCategory::General Principles
Prompt [[Prompt::A research group is trying to study the effects of a short course of concentrated coffee bean extract on weight loss in healthy volunteers. They design a randomized double-blinded controlled trial and recruit 154 subjects. Subjects are randomized in into 2 groups one receiving 3 daily doses of coffee bean extract and the other receiving 3 daily doses of a placebo. At the end of the 6 month period, the biostatistician wants to compares the mean change in body weight from baseline in the 2 groups. Which of the following tests should the biostatistician use in order to obtain a valid comparison?]]
Answer A AnswerA::Chi-square
Answer A Explanation [[AnswerAExp::Chi-square is a test which allows to determine a difference between 2 or more proportions or percentages of categorical outcomes.]]
Answer B AnswerB::ANOVA
Answer B Explanation [[AnswerBExp::ANOVA or analysis of variance allows to determine if a difference exists between the means of 3 or more groups. ANOVA (Analysis of Variance of 3 or more groups).]]
Answer C AnswerC::T-test
Answer C Explanation [[AnswerCExp::T-test allows to check for difference between the means of 2 groups.]]
Answer D AnswerD::Pearson correlation
Answer D Explanation [[AnswerDExp::Pearson correlation is a coefficient which allows to determine relationship, not to determine if statistical significance is achieved. It does not allow to determine causality. The relationship could be represented graphically; the more solid the line represented, the stronger the correlation. This correlation could vary from +1 to -1; varying from a directional relationship or inverse relationship respectively. The closer the absolute value to 1, the stronger the correlation being graphically represented as a line.]]
Answer E AnswerE::Power measure
Answer E Explanation AnswerEExp::Power measure
Right Answer RightAnswer::C
Explanation [[Explanation::

Educational Objective: T- test is used to check if a difference exists between the means of 2 groups.
References: ]]

Approved Approved::Yes
Keyword
Linked Question Linked::
Order in Linked Questions LinkedOrder::
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