# Probability, confidence and expected value

> What the numbers in an answer mean, and what they do not.

## Probabilities

Every answer gives a probability for each option: how likely Eevo thinks it is that the option is the best one for the stakeholder. They add up to 1. `confidence` is simply the probability of the best option. A best option at 0.9 means Eevo clearly prefers it. A best option at 0.45 out of three means the options are close, and whoever reports the answer should say so.

These are probabilities about which option is best, not about what will happen. "0.74 for shipping now" does not mean shipping succeeds 74% of the time. It means Eevo, given the context, is fairly sure shipping now is the better choice for that stakeholder.

## Typed questions

A `choice` and a `score` work the same way: a probability for each label or level. A `noul` is the probability that a statement is true. Because the numbers are probabilities, your code can act on them directly: act automatically above a threshold you pick, and ask a person below it.

## Expected value (Default mode)

In Default mode each option has an expected value: the sum of its consequences' sizes, benefits positive and harms negative. Eevo sizes each consequence as if it happens; there is no separate probability. Sizes are on the stakeholder's own scale, where the largest consequence is 1. So an EV of 0.5 means "about half as good as the largest consequence on the list is big".

- Compare EVs within a stakeholder. Across stakeholders the scales differ, so the numbers are not comparable.
- The p10–p90 range shows how sure Eevo is about the sizes. Overlapping ranges mean the options are close.
- `p_best` is the share of 1,000 draws over that uncertainty in which an option comes out highest. It is Default mode's equivalent of the Direct probabilities.