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The Theoretical Relationship between Sample Size and Expected Predictive Precision for EQ-5D Valuation Studies: A
Kelvin K W Chan1,2,3,4, Eleanor M Pullenayegum5,4
1Sunnybrook Odette Cancer Centre, University of Toronto, Toronto, ON, Canada.
We developed a formula to estimate the mean square error (MSE) for multi-attribute utility instruments (MAUI) scoring algorithms. Increasing sample size improves accuracy up to 300-500 participants, after which adding more health states is more beneficial.
Area of Science:
- Health Economics
- Psychometrics
- Biostatistics
Background:
- Scoring algorithms for multi-attribute utility instruments (MAUI) are subject to uncertainty due to their development in valuation studies.
- Designing valuation studies with adequate sample sizes is crucial for achieving reliable accuracy in MAUI scoring.
- Existing methods do not fully account for the inherent uncertainty and model-fit limitations in MAUI valuation.
Purpose of the Study:
- To derive the first closed-form mathematical formula for the mean square error (MSE) of additive MAUI scoring algorithms.
- To express MSE as a function of sample size and the number of directly valued health states.
- To provide a tool for optimizing the design of MAUI valuation studies for desired predictive precision.
Main Methods:
- Derived a closed-form MSE formula based on the EQ-5D valuation study design.
- Incorporated sample size and the number of valued health states (overall and per subject) into the formula.
- Validated the formula using a simulation study on the US EQ-5D-3L dataset, assessing model fit and data characteristics (random-effects vs. OLS, heteroscedasticity).
Main Results:
- The derived MSE formula was validated across different statistical models and assumptions (random-effects vs. OLS, heteroscedasticity vs. homoscedasticity).
- Mean square error (MSE) plateaus asymptotically as sample size increases, rather than approaching zero.
- Significant MSE improvement is observed with increasing sample size for smaller samples (up to 300-500); beyond this, increasing the number of health states offers greater precision gains.
Conclusions:
- A closed-form formula for calculating the MSE of additive MAUI scoring algorithms has been successfully derived.
- The formula quantifies the impact of sample size and the number of health states on predictive precision.
- This provides MAUI valuation study developers with a method to determine optimal sample sizes for achieving specific accuracy targets.
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