{
  "slug": "survival-function",
  "term": "Survival function",
  "aliases": [
    "Reliability function",
    "Survivor function"
  ],
  "definition": "The survival function S(t) = P(T > t) is the probability that a time T to a defined event exceeds t, measured from a specified time origin.",
  "note": "Specify the drive population, failure event, time origin and units. S(t) is dimensionless and equals 1 - F(t); it is not an annualized event rate. [nist-survival] For a drive surviving to age a, survival for another u units of time is S(a + u) / S(a), for u >= 0 and S(a) > 0, using the same population and time origin. This follows from conditional probability, not a constant-hazard assumption.",
  "related": [
    "hazard-rate",
    "right-censoring",
    "left-truncation",
    "kaplan-meier-estimator",
    "afr"
  ],
  "citations": [
    {
      "id": "nist-survival",
      "title": "NIST e-Handbook 8.1.2.2: Reliability or survival function",
      "url": "https://www.itl.nist.gov/div898/handbook/apr/section1/apr122.htm",
      "accessed": "2026-10-13"
    }
  ],
  "status": "shipping",
  "advantages": [],
  "limitations": [],
  "supersedes": [],
  "supersededBy": [],
  "firstSeen": null,
  "lastSeen": null,
  "updated": "2026-10-13"
}