# Question types

> The three question types of the Decision API: noul for yes or no with a probability, choice for one of several labels, and score for a level on a scale.

Section: Concepts. Web page: https://www.launchables.ai/docs/question-types

Every question has a `type`, the `instructions` (the question itself, in plain language) and, for `choice` and `score`, the `criteria` that list the options. Each question is read separately against the same state.

## noul: yes or no

Optional `criteria` describe what each answer means, under `true` and `false` (or `yes` and `no`). Give both sides, or neither. A side may be `null`, and is then shown as "Yes" or "No". The response gives `noul`, the probability of yes.

```
"eligible": {
  "type": "noul",
  "instructions": "Does the applicant meet the residency rule?",
  "criteria": {
    "true": "Lived in the UK for at least 3 of the last 5 years",
    "false": "Residency not shown, or under 3 years"
  }
}
```

```
"eligible": { "type": "noul", "noul": 0.87 }
```

**Yes/no answers are committed: probabilities for uncertain answers are reported as at least 0.80 towards the chosen side.** When the model's own probability of yes falls between 0.2 and 0.8, the answer goes to its more likely side and is reported at one fixed probability, 0.801 today, so `noul` is never between 0.2 and 0.8. Answers outside that range are returned as read. A committed answer is less certain than its number: on our own held-out cases, committed answers are right about 70% of the time, not 80%. See [Thresholds](https://www.launchables.ai/docs/thresholds) for where to set yes/no thresholds.

## choice: one of several labels

`criteria` maps each label to a short description, or is a list of labels. A description may be `null` when the label says it all (`{"calm": null, "upset": null}`). The response gives the chosen label, its `confidence` and a probability for every label. Up to 26 labels per question: the options are read as letters A to Z in one pass.

```
"route": {
  "type": "choice",
  "instructions": "Which team should handle this message?",
  "criteria": {
    "billing": "Payments, invoices and refunds",
    "returns": "Returning or exchanging an item",
    "technical": "The product does not work",
    "other": "Anything else"
  }
}
```

```
"route": {
  "type": "choice",
  "choice": "returns",
  "confidence": 0.83,
  "probabilities": { "billing": 0.06, "returns": 0.89, "technical": 0.01, "other": 0.04 }
}
```

## score: a level on an ordered scale

`criteria` is a list of level descriptions, lowest first; levels are numbered from 0. The response gives the most likely `level`, the probability-weighted `score`, a `confidence`, a `legend` (each level's description, by number) and a probability for every level.

```
"priority": {
  "type": "score",
  "instructions": "How urgent is this complaint?",
  "criteria": ["Routine", "Needs a reply this week", "Needs a reply today", "Safety risk, act now"]
}
```

```
"priority": {
  "type": "score",
  "score": 1.92,
  "level": 2,
  "confidence": 0.81,
  "legend": { "0": "Routine", "1": "Needs a reply this week", "2": "Needs a reply today", "3": "Safety risk, act now" },
  "probabilities": { "0": 0.03, "1": 0.12, "2": 0.75, "3": 0.10 }
}
```

## Confidence

`confidence` runs from 0 to 1 and is our own measure of how settled an answer is. It is not a probability that the answer is right; for that, read `probabilities`.

- **choice:** the probability of the chosen label minus that of the runner-up. 0 is a tie at the top; 1 puts everything on one label.
- **score:** 1 minus the expected distance from the middle (median) level, divided by half the scale. Being unsure between neighbouring levels lowers it a little; being split between the two ends of the scale makes it 0.
- **noul** answers have no `confidence`: the probability of yes already says it.

## Choosing a type

- Use `noul` for a single rule or check: is it allowed, is it present, is it supported.
- Use `choice` when exactly one of several labels applies: a team, a category, a tool.
- Use `score` when the options are ordered and being one level out matters less than being three out: urgency, risk, severity.