WBR0435
| Author | [[PageAuthor::Rim Halaby, M.D. [1]]] |
|---|---|
| Exam Type | ExamType::USMLE Step 1 |
| Main Category | MainCategory::Biostatistics/ Epidemiology |
| Sub Category | SubCategory::Renal |
| Prompt | [[Prompt::A researcher is conducting a cross-sectional study to identify factors that are associated with hemodialysis adequacy in a group of 90 patients undergoing hemodialysis. After data collection, statistical analysis reveals that after precise measurement of the urea reduction rate (URR), URR is associated with hemodialysis adequacy with a p-value of 0.12 at a 95% confidence interval. Which of the following modifications will most likely increase the power of the association in the study conducted by this researcher?]] |
| Answer A | AnswerA::Recruiting more hemodialysis patients to the study |
| Answer A Explanation | AnswerAExp::Recruiting more patients to the study that fit the inclusion criteria can increase the power of the study. |
| Answer B | AnswerB::Recruiting 90 peritoneal dialysis patients to the study |
| 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 power. |
| Answer C | AnswerC::Changing the confidence interval to 92% |
| Answer C Explanation | AnswerCExp::Decreasing the confidence interval will most likely increase the associated factors; but the power of the study will not increase. |
| Answer D | AnswerD::Repeating all measurements of urea reduction rate 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 study’s power is not expected to be affected. |
| Answer E | AnswerE::Power of the study cannot be changed |
| Answer E Explanation | AnswerEExp::Power of the study can in fact be changed if the sample size is increased. |
| Right Answer | RightAnswer::A |
| Explanation | [[Explanation::Power of the study is defined as: Power = (1-β), where β is the type II error – defined as perceiving there is no effect when in fact there is. Power of the study is dependent on the size of the study population. As such, adding more hemodialysis patients to the study will most likely increase the power of the study.
Educational Objective:
Power of the study is defined as: Power = (1-β), where β is the type II error. Power can be increased when the sample size of the enrolled patients increases. |
| Approved | Approved::No |
| Keyword | WBRKeyword::urea reduction rate, WBRKeyword::hemodialysis, WBRKeyword::power, WBRKeyword::type II, WBRKeyword::error, WBRKeyword::sample, WBRKeyword::size, WBRKeyword::confidence, WBRKeyword::interval |
| Linked Question | Linked:: |
| Order in Linked Questions | LinkedOrder:: |