C.16.RM:4.2 - Locate the contribution that could change the answer
Follow the target-to-indication relation far enough to identify the consequential influence or incompatible operation. Ask what each candidate explanation would require changing and what present information bears on it.
| Possible repair location | What to inspect | A useful change |
|---|---|---|
| Subject model | Which interaction, boundary or varying condition is omitted from the predicted quantity? | Include a background contribution or the dependence on the actual preparation. |
| Instrument model | How does the instrument respond in the range and conditions used? | Include loading, offset, saturation or a calibrated nonlinear response. |
| Computation | Does the implemented operation evaluate the intended relation with its units, domains and required accuracy? | Correct a unit conversion, retained branch, numerical approximation or aggregation interval. |
| Subject arrangement | Can a relevant condition be controlled while retaining the target or a usable relation to it? | Shield an unwanted input or hold a consequential condition stable. |
| Measuring arrangement | Can a different interaction or indication distinguish the needed alternatives? | Change the input resistance, operating range, observation timing or reference measurement. |
The table locates choices; the domain Method supplies the physical law or diagnosis that makes one choice appropriate. A common influence can cross several rows. For example, a change in illumination can alter both the subject response and the detector response.
For a suspected computational fault, run a supplied or constructed input whose answer follows from the intended relation. Compare intermediate values, units and branch choices until the divergence is located. A successful calculation on that input checks implementation of the relation. Compare the relation with the actual subject separately when its adequacy is in question.