Plan from the supplied facts
Original information says effort is either 2 or 8 hours, with no probabilities. Two hypothetical models below both respect those outcomes but give different chances of being no greater than 4 hours. Neither model is established by the bounds.
| Model | Probability of 2 h | Probability of 8 h | Chance ≤4 h |
|---|---|---|---|
| Possible M1 | 0.9 | 0.1 | 0.9 |
| Possible M2 | 0.1 | 0.9 | 0.1 |
| Known evidence | Unknown | Unknown | Not determined |
Work through the choice
Only the 2-hour outcome meets the 4-hour threshold. Since its probability is unknown, the threshold chance is unknown too. A midpoint is not a probability model.
Can the planner say there is a 50% chance from the original two outcomes alone?
Show the worked answer
No. Equal weighting would be an additional assumption. M1 and M2 already demonstrate different answers consistent with the same outcomes.
Material to use in your plan
Separate permitted outcomes, supplied probabilities and the requested threshold. If probability inputs are absent, record “likelihood undetermined” and the evidence needed to estimate it.