Power Vs. Precision When Estimating Risk Differences Using Observational Data? A Case Study From TARGET-IBD.

Challenge

Real-world studies using IPTW often rely on power calculations from RCT frameworks assuming randomization, which are inappropriate for observational settings where confounding adjustment inflates variance—leaving researchers without guidance on whether to prioritize power or precision in study design.

Solution

Target RWE biostatisticians conducted a simulation study using TARGET-IBD data to compare power- and precision-based sample size frameworks under varying confounding levels, quantifying variance inflation factors from IPTW.

Impact

Providing an empirical framework for choosing between power- and precision-based sample size approaches in IPTW studies enables more appropriate design decisions, reducing the risk of underpowered or miscalibrated real-world comparative effectiveness studies.