WBR0435: Difference between revisions
Jump to navigation
Jump to search
Sergekorjian (talk | contribs) No edit summary |
Sergekorjian (talk | contribs) No edit summary |
||
| Line 21: | Line 21: | ||
|MainCategory=Biostatistics/Epidemiology | |MainCategory=Biostatistics/Epidemiology | ||
|SubCategory=Renal | |SubCategory=Renal | ||
|Prompt=A researcher conducts a cross-sectional study to identify factors that are associated with hemodialysis adequacy among 90 patients undergoing hemodialysis. Following data collection, statistical analysis reveals that the urea reduction rate (URR) is associated with hemodialysis adequacy with a p-value of 0.12. Which of the following modifications will most likely increase the statistical power of the study? | |Prompt=A researcher conducts a cross-sectional study to identify factors that are associated with hemodialysis adequacy among 90 patients undergoing hemodialysis. Following data collection, statistical analysis reveals that the urea reduction rate (URR) is associated with hemodialysis adequacy with a p-value of 0.12 (significant p-value <0.05). Which of the following modifications will most likely increase the statistical power of the study? | ||
|Explanation=The statistical power of a study is defined as: Power = (1-β), where β is the type II error (perceiving there is no effect when there actually is). The power of the study is dependent on the sample size. Increasing the number of [[hemodialysis]] patients enrolled in the study will increase the power. | |Explanation=The statistical power of a study is defined as: Power = (1-β), where β is the type II error (perceiving there is no effect when there actually is). The power of the study is dependent on the sample size. Increasing the number of [[hemodialysis]] patients enrolled in the study will increase the power. | ||
[[File: | [[File: Power.png|700px]] | ||
|AnswerA=Recruiting more hemodialysis patients to the study | |AnswerA=Recruiting more hemodialysis patients to the study | ||
|AnswerAExp=Recruiting more patients, who fit the inclusion criteria, can increase the statistical power of the study. | |AnswerAExp=Recruiting more patients, who fit the inclusion criteria, can increase the statistical power of the study. | ||
|AnswerB= | |AnswerB=Comparing peritoneal dialysis patients to hemodialysis patients | ||
|AnswerBExp=Since the study does not involve peritoneal dialysis patients, adding those to the study is not appropriate and will most likely limit the study’s statistical power. | |AnswerBExp=Since the study does not involve peritoneal dialysis patients, adding those to the study is not appropriate and will most likely limit the study’s statistical power. | ||
|AnswerC= | |AnswerC=Increasing the p-value cut-off to <0.01 | ||
|AnswerCExp= | |AnswerCExp=Increasing the p-value cut-off to <0.01 will decrease the statistical power of the study. | ||
|AnswerD=Repeating all measurements of urea reduction rate (URR) for the 90 patients who are recruited | |AnswerD=Repeating all measurements of urea reduction rate (URR) for the 90 patients who are recruited | ||
|AnswerDExp=Repeating measurements will test the precision of the study’s measurements. Since measurements were described as precise in the first place, the statistical power of the study is likely not to be affected. | |AnswerDExp=Repeating measurements will test the precision of the study’s measurements. Since measurements were described as precise in the first place, the statistical power of the study is likely not to be affected. | ||
|AnswerE=The statistical power of the study cannot be changed | |AnswerE=The statistical power of the study cannot be changed | ||
|AnswerEExp=The statistical power of the study can be changed if the sample size is increased. | |AnswerEExp=The statistical power of the study can be changed if the sample size is increased. | ||
|EducationalObjectives=Statistical power of a study is defined as: Power = (1-β), where β is the type II error. | |EducationalObjectives=Statistical power of a study is defined as: Power = (1-β), where β is the type II error. The power increases when the study sample size increases, or when the significance level is lowered. | ||
|References=First Aid 2014 page 57 | |References=Rosner B. Fundamentals of Biostatistics. Cengage Learning; 2010.<br> | ||
First Aid 2014 page 57 | |||
|RightAnswer=A | |RightAnswer=A | ||
|WBRKeyword=Urea reduction rate, URR, Hemodialysis, Statistical power, Power, Type II, Error, Sample size, Confidence, Interval, Confidence interval | |WBRKeyword=Urea reduction rate, URR, Hemodialysis, Statistical power, Power, Type II, Error, Sample size, Confidence, Interval, Confidence interval | ||
|Approved=Yes | |Approved=Yes | ||
}} | }} | ||
Revision as of 21:27, 17 September 2014
| Author | [[PageAuthor::Yazan Daaboul, M.D. (Reviewed by Alison Leibowitz)]] |
|---|---|
| Exam Type | ExamType::USMLE Step 1 |
| Main Category | MainCategory::Biostatistics/Epidemiology |
| Sub Category | SubCategory::Renal |
| Prompt | [[Prompt::A researcher conducts a cross-sectional study to identify factors that are associated with hemodialysis adequacy among 90 patients undergoing hemodialysis. Following data collection, statistical analysis reveals that the urea reduction rate (URR) is associated with hemodialysis adequacy with a p-value of 0.12 (significant p-value <0.05). Which of the following modifications will most likely increase the statistical power of the study?]] |
| Answer A | AnswerA::Recruiting more hemodialysis patients to the study |
| Answer A Explanation | AnswerAExp::Recruiting more patients, who fit the inclusion criteria, can increase the statistical power of the study. |
| Answer B | AnswerB::Comparing peritoneal dialysis patients to hemodialysis patients |
| Answer B Explanation | AnswerBExp::Since the study does not involve peritoneal dialysis patients, adding those to the study is not appropriate and will most likely limit the study’s statistical power. |
| Answer C | [[AnswerC::Increasing the p-value cut-off to <0.01]] |
| Answer C Explanation | [[AnswerCExp::Increasing the p-value cut-off to <0.01 will decrease the statistical power of the study.]] |
| Answer D | AnswerD::Repeating all measurements of urea reduction rate (URR) for the 90 patients who are recruited |
| Answer D Explanation | AnswerDExp::Repeating measurements will test the precision of the study’s measurements. Since measurements were described as precise in the first place, the statistical power of the study is likely not to be affected. |
| Answer E | AnswerE::The statistical power of the study cannot be changed |
| Answer E Explanation | AnswerEExp::The statistical power of the study can be changed if the sample size is increased. |
| Right Answer | RightAnswer::A |
| Explanation | [[Explanation::The statistical power of a study is defined as: Power = (1-β), where β is the type II error (perceiving there is no effect when there actually is). The power of the study is dependent on the sample size. Increasing the number of hemodialysis patients enrolled in the study will increase the power.
|
| Approved | Approved::Yes |
| Keyword | WBRKeyword::Urea reduction rate, WBRKeyword::URR, WBRKeyword::Hemodialysis, WBRKeyword::Statistical power, WBRKeyword::Power, WBRKeyword::Type II, WBRKeyword::Error, WBRKeyword::Sample size, WBRKeyword::Confidence, WBRKeyword::Interval, WBRKeyword::Confidence interval |
| Linked Question | Linked:: |
| Order in Linked Questions | LinkedOrder:: |
