Calculating the Expected Value of Sample Information for Observational Studies affected by Confounding
Existing Expected Value of Sample Information (EVSI) methods rely on idealized randomized controlled trial assumptions, rendering them incapable of evaluating observational data affected by confounding bias. This study proposes a controllable confounded data generation framework based on Inverse Target Trial Emulation (ITTE), integrating inverse probability weighting and regression approaches to compute the EVSI of observational data. Furthermore, an efficient algorithm is developed to determine the sample size required to recover the EVSI achievable under an ideal randomized design. Empirical validation confirms that the EVSI of adjusted observational data remains lower than that of randomized data and decreases monotonically as confounding severity increases. By extending value-of-information analysis to more realistic scenarios, this work provides a novel methodological framework for assessing the value of observational studies.