In the INSPIRES study, patients were randomized to receive dual antiplatelet therapy (DAPT) or aspirin alone for 21 days within 72 hours after a stroke or TIA. The primary endpoint (new stroke) occurred in 7.3% of patients with DAPT and 9.2% with aspirin alone (HR 0.79, 95% CI 0.66 to 0.94). Which of the following best describes the interpretation of the primary endpoint?

Which of the following scenarios will reduce the statistical power of a clinical trial?

A clinical trial was conducted comparing ivermectin versus placebo for severe COVID-19 pneumonia. The primary endpoint (28-day mortality) was not different between the two treatment arms. Multiple secondary endpoints were also not significantly different between the two groups. A post-hoc subgroup analysis of patients with SpO2 values less than 89% at randomization did demonstrate a reduction in ICU length of stay by 18 hours (p=0.03). Which of the following best describes a limitation of the ICU length of stay subgroup analysis?

An investigator plans to compare methylprednisolone versus dexamethasone for severe community-acquired pneumonia. Patients were included if they were 18-65 years of age and not immunocompromised. The study will analyze the impact of the study drug on hospital mortality. What variable in this study is the independent variable?

A study investigating the efficacy of a new drug reported the mean change in symptom severity of -1.5 (95% CI -2.5 to -0.5). What is the correct interpretation of this confidence interval?

In a retrospective study, an investigator is evaluating whether patients who routinely take a statin medication are more likely to experience new-onset atrial fibrillation (NOAF) during hospitalization for pneumonia. The results showed that 0 out of 50 patients with prior statin therapy experienced NOAF but 2 out of 50 (4%) of patients without statin therapy experienced NOAF. What statistical test is most appropriate to compare these two groups?

In the ANNEXA-I study, patients with intracerebral hemorrhage receiving factor Xa inhibitor anticoagulants were randomized to receive either andexanet alfa or usual care. The primary safety endpoint, thrombotic events, occurred in 10.3% of patients randomized to andexanet and 5.6% of patients in the usual care arm (p=0.048). What is the number needed to harm for thrombotic events with andexanet alfa?

An investigator wants to identify risk factors of hospital-acquired Clostridioides difficile-associated diarrhea (CDAD). Age, days of IV antibiotics, use of a proton pump inhibitor, and use of probiotics are all potential predictors of CDAD. Which statistical analysis would be most appropriate for this study design?

A study was conducted to evaluate the impact of a pharmacy student calling patients after a heart failure hospitalization to discuss their medications. One endpoint of the trial was the total healthcare cost over 12 months, which included medications, clinic visits, and hospitalizations. A convenience sample of 100 patients from one year ago was compared to 100 patients who received the intervention with a pharmacy student. Upon further analysis, the "healthcare cost" endpoint was non-parametric and significantly right skewed. What statistical test would be most appropriate to compare healthcare costs between those who received and did not receive the intervention?

In the TECOS trial, patients with type II diabetes were randomized to receive sitagliptin or placebo. The trial was designed to assess whether sitagliptin was non-inferior to placebo for composite cardiovascular events with a non-inferiority margin hazard ratio of 1.3. After enrolling 14,671 patients, composite cardiovascular events occurred in 11.4% of patients receiving sitagliptin and 11.6% of patients receiving placebo (HR 0.98, 95% CI 0.88 to 1.09, p