Paeds Vivas · professional-practice-and-evidence
Reading a statistical result — branching viva
Viva on reading and defending the interpretation of a paediatric statistical result — confidence interval, p-value, test choice, regression and survival output.
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Target exams
RACP DCEMRCPCH ClinicalRCPSC Pediatrics
Prompt
Journal club: you are given an abstract of a paediatric trial reporting a mean difference in symptom duration with a p-value of 0.04 but a 95 percent confidence interval that is wide and crosses zero. A second abstract reports a hazard ratio of 0.6 (95 percent confidence interval 0.45 to 0.80) for relapse-free survival, and a logistic regression model that ran twenty subgroup analyses.
Opening (candidate)
I would treat this as a structured reading of the effect size and its confidence interval before I read the p-value. First I would classify the data and check that the right test was used, then I would read the confidence interval against the null, then interpret the p-value in context, and finally judge clinical importance and applicability to the child. A p-value on its own never carries the weight of those judgements. [9] [4]
References5ShowHide
- [2]Bland JM, Altman DG Multiple significance tests: the Bonferroni method. BMJ, 1995.PMID 7833759
- [3]Akobeng AK Understanding type I and type II errors, statistical power and sample size. Acta Paediatr, 2016.PMID 26935977
- [4]Sullivan GM, Feinn R Using Effect Size-or Why the P Value Is Not Enough. J Grad Med Educ, 2012.PMID 23997866
- [7]Cortés J, González JA, Campbell MJ, Cobo E A hazard ratio was estimated by a ratio of median survival times, but with considerable uncertainty. J Clin Epidemiol, 2014.PMID 25063554
- [9]Altman DG, Bland JM How to obtain the confidence interval from a P value. BMJ, 2011.PMID 21824904