Forensic Interlaboratory Reference Delta Tool

Description

Return first-minus-second and divide by their hypotenuse.

Forensic measurement calculations require a known calibration, geometric model and uncertainty convention. A converted length, ratio or residual describes the supplied measurements; it does not establish common origin, identity or evidentiary strength.

Return first-minus-second and divide by their hypotenuse.

When to use this tool

Use Forensic Interlaboratory Reference Delta when you need an explicit image or physical-measurement term.

How to use the tool and how it works

Enter first, second, firstUncertainty, secondUncertainty. Use the units and conventions below.
Run the tool. Correct any format, range, or cross-field input error before interpreting the output.
Read difference, normalizedDifference. Use the output convention below.

Require nonnegative uncertainties with positive sum. Return first-minus-second and divide by their hypotenuse.^[1]

Input field	Meaning and units	Accepted input
first	First	Required. Finite number.
second	Second	Required. Finite number.
firstUncertainty	First Uncertainty	Required. Finite number; minimum 0.
secondUncertainty	Second Uncertainty	Required. Finite number; minimum 0.

Output field	Interpretation	Returned shape
difference	Difference	Required. Finite number.
normalizedDifference	Normalized Difference	Required. Finite number.

json

{
  "input": {
    "first": 105,
    "second": 100,
    "firstUncertainty": 3,
    "secondUncertainty": 4
  },
  "output": {
    "difference": 5,
    "normalizedDifference": 1
  }
}

Limitations and assumptions

The root-sum-square denominator assumes the intended uncorrelated uncertainty convention. It is not automatically a significance test, acceptance limit, or probability of source identity.
Inputs must satisfy both the field types and the cross-field conditions above. Invalid input causes an error; a successful false flag or documented placeholder is a different result.
Numeric calculations use binary floating point unless exact decimal-integer arithmetic is explicitly stated. No hidden measurement tolerance or decimal rounding is added; nonfinite or out-of-contract results are rejected. Numeric signed-zero results are exported as zero.

Alternative or Complementary methods

Use the validated measurement method and original evidence for interpretation. Include calibration, geometry, uncertainty and the full evidentiary context rather than turning a numerical match into an identification.

References

Calculation and input contract: forensic-science/forensic-interlaboratory-reference-delta — tool.io

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