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What is the Duplicate Entrance Score?

The Duplicate Entrance Score (DES) detects whether a respondent is likely a duplicate of another recent entrant in the same survey. It compares demographics and, when available, IP address against peers who entered shortly before. DES is available for API v3 projects only. It is not supported on v1/v2 addRespondent requests.

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High-level checks performed

  • Requires at least 4 demographic fields to compute a valid score. Fewer than 4 demographics are accepted but scored as invalid (N/A).
  • Accepts up to 10 demographics. Each demographic type must be unique (use custom type strings instead of repeating "other").
  • Compares the current entrant against peers from the last 15 minutes (up to a minimum of 10 peers when available; fewer peers still compared).
  • If no peers exist (first entrant in the window), the score is 100 (VALID_ENTRANT).
  • If any peer shares the same IP, the score is 0 (DUPLICATE_IP) and peer respondent IDs are returned.
  • Otherwise, demographics are compared per peer. Exact matches keep a low (duplicate-like) score; similar age / year of birth can add a limited penalty; any hard mismatch treats that peer as different. The final score is the minimum over peers.
  • Scores below 40 are categorized as DUPLICATE_ENTRANT; otherwise VALID_ENTRANT.

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Demographic types

type is a free-form string. Any custom label is allowed and compared with exact match (case-insensitive after trim), except the age-like types below. Recommended type values Age-like types (age, yearOfBirth) These are the only types that use similarity instead of exact match:
  • Numeric answers within ±3 count as similar (adds a limited score penalty once per peer, even if both age and yearOfBirth are similar)
  • Exact numeric matches count as same
  • Non-numeric or larger differences count as different (that peer is treated as fully different)
All other types — including recommended values above and any custom string — always use exact match.

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Categories

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Default cleaning

When cleaning is enabled with recommended settings:
  • Exclude respondents with a DES score below 40
  • Category-based DES exclusions (DUPLICATE_IP, DUPLICATE_ENTRANT) are off by default

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How to use the DES?

Send a single DES data point on POST /v3/addRespondent with optional entranceTime (defaults to the current timestamp if omitted), optional ip, and a demographics array. Only one DES data point is allowed per respondent (dataPointId defaults to "DES").