Source: https://guthlabs.ai/docs/instruments/nnt-nnh-number-needed-to-treat-harm/implementation/

instrument implementation / implementation-contract

# NNT/NNH (Number Needed to Treat/Harm) implementation

A source-bound implementation contract for NNT/NNH (Number Needed to Treat/Harm); deployment and executable qualification remain separate.

Status: **VERIFIED_CLEAN**Lifecycle: **implementation-contract**

## Binding contract

This record describes what an executable surface must bind and validate. It does not claim that a public calculator, package, or production route is deployed.

**Record owner**: Guth Instruments

**Lifecycle**: verified-clean

**Evidence ID**: t5-181

**Effect**: Computation or source lookup only

## Input and validation requirements

Equal control and experimental event rates produce ARR=0, so NNT and NNH require division by zero and are undefined. The specification also lists RRR as an output without defining its formula or sign convention, creating a convention-dependent result.

## Required corrections

No binding erratum is attached to this unique-name record. Implementers must still preserve the declared units, domain, and failure behavior.

## Inspectable interface fixture

The sample below is evidence for interface and validation tests, not a production implementation.

````
{
  "inputs": {
    "CER": 0.2,
    "EER": 0.15
  },
  "expected_outputs": {
    "ARR": 0.05,
    "RRR": 0.25,
    "NNT_raw": 20,
    "NNT_reported": 20,
    "NNH": null
  },
  "working": "ARR=|0.20−0.15|=|0.05|=0.05. Because EER<CER, this is benefit, so RRR=(0.20−0.15)/0.20=0.05/0.20=0.25=25%. NNT=1/0.05=20, so reported NNT=20. NNH is not applicable because the experimental event rate is lower."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/nnt-nnh-number-needed-to-treat-harm/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/nnt-nnh-number-needed-to-treat-harm/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/nnt-nnh-number-needed-to-treat-harm/qualification/>)

## Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

- `VERIFIED_LEDGER.json`

- `evidence-tranche5/tranche5-results.json`