Expected Net Benefit and Probability Explorer
Change the probability, cost and QALYs for two possible scenarios. The explorer shows why winning more often is not always the same as producing the greatest expected net benefit.
Version 1.0 · Copyright © 2026 Darrin Baines IP Limited. All rights reserved.
What the explorer calculates
Net monetary benefit equals the threshold multiplied by QALYs minus cost. Expected net benefit is the probability-weighted average across the two scenarios, while probability of cost-effectiveness records how often an alternative has the greater net benefit.
NMB = threshold × QALYs − cost | Expected NMB = Σ(probability × scenario NMB)
Enter the decision inputs
Both scenario probabilities must total 100%. Costs and QALYs are illustrative inputs for each alternative, and the same threshold is applied throughout.
What these defaults show
Alternative A wins narrowly in the more likely scenario. Alternative B wins by much more in the other scenario, allowing expected value and probability to produce different rankings.
Compare expected value with probability
The expected-net-benefit decision rule selects the alternative with the greatest expected NMB. Probability of cost-effectiveness is still useful, but it describes uncertainty rather than replacing the expected-value decision.
| Scenario | Probability | NMB A | NMB B | Scenario winner |
|---|
Important limits
This is an educational two-scenario example, not a reimbursement model. A real evaluation should use the complete probability distribution, relevant alternatives, validated evidence, appropriate uncertainty analysis and the applicable institutional decision process.
- The greatest expected net benefit identifies the preferred alternative under the stated economic rule.
- The probability of cost-effectiveness shows how often an alternative wins, not the size of its gains or losses.
- Cost-effectiveness does not establish affordability, equity, feasibility or adoption.