Descriptive & Inferential Biostatistics, Hypothesis Testing, and Sample Size Estimation — WACS Viva & Clinical Scenarios (Statistics & Evidence-Based Practice)

Exam-style descriptive & inferential biostatistics, hypothesis testing, and sample size estimation viva scenarios with examiner probes and model answers for…

Scenarios covered

• SCENARIO 1: Scenario 1: You are reviewing a draft proposal for a prospective, randomised study in your department comparing recovery times (in minutes) between propofol-based total intravenous anaesthesia (TIVA) and isoflurane inhalational anaesthesia for elective day-case laparoscopies. The preliminary pilot data in 15 patients shows a marked positive skew in recovery times. As the departmental academic registrar, how do you determine the appropriate descriptive statistics, normality tests, and inferential hypothesis testing framework for this study?
• SCENARIO 2: Scenario 2: A published multicentre trial in a major anaesthetic journal investigates the addition of dexmedetomidine to bupivacaine for transversus abdominis plane (TAP) blocks in adult patients undergoing emergency exploratory laparotomy for peritonitis. The authors report a statistically significant reduction in 24-hour morphine consumption (p = 0.042; mean difference 2.1 mg; 95% Confidence Interval 0.1 to 4.1 mg). How do you critically interpret the statistical and clinical significance of this result for your West African clinical practice?
• SCENARIO 3: Scenario 3: You are designing a randomised equivalence trial comparing a generic, locally sourced bupivacaine preparation against an established imported reference formulation for spinal anaesthesia in elective orthopaedic surgery. How do you formulate the null and alternative hypotheses, establish the equivalence margin (delta), and calculate the required sample size ensuring protection against Type I and Type II errors?
• SCENARIO 4: Scenario 4: An observational study is conducted in your tertiary institution analyzing mortality rates among obstetric patients admitted to the ICU with severe pre-eclampsia versus eclampsia. The outcome data is presented in a two-by-two contingency table where one of the cells (eclamptic maternal deaths) contains an expected count of 3 patients. Outline your approach to statistical test selection for categorical association and discuss the handling of sparse contingency tables.