Understanding confidence evaluation

At runtime, the Dialog service handles confidence scores that VoiceXML Connector relays from your recognition engine (Nuance Recognizer or Dragon Voice) along with recognition results. When there are multiple results, the Dialog service chooses the best one, based on context and confidence score. The Dialog service then uses the applicable Confirmation strategy type, Confidence-high threshold, and Confidence-low threshold, to evaluate whether to accept the result, reject it, or elicit a confirmation turn. In Mix.dialog, you can find the thresholds and confirmation strategy types in your project settings.

At collection turns:

  • If the confidence score of the collected utterance is lower than the Confidence-low threshold, the recognition result is rejected without confirmation. This generates a nomatch event.
  • If the confidence score of the collected utterance is lower than the Confidence-high threshold but higher than Confidence-low, confirmation is triggered, unless the confirmation strategy type is Never, in which case the result is accepted without confirmation.
  • If the confidence score of the collected utterance equals or is higher than the Confidence-high threshold, the recognition result is accepted without confirmation.
  Example of confidence thresholds settings for collection turns  

At confirmation turns, if the confidence score of the collected utterance is lower than the applicable Confidence-low threshold, the recognition result is rejected, and this generates a nomatch event.

  Example of confirmation strategy and confidence threshold settings for confirmation turns  

The global confirmation strategy type is Never, by default. You can change the global strategy, or set a different confirmation strategy for specific channels, or for specific entities.

  Example of confirmation strategy setting for a specific entity  

You can also set confidence thresholds by language, for collection or for confirmation, for specific channels, or for specific entities.

  Example of confidence threshold settings for a specific entity