MMP.14:1 - Problem frame

Use this pattern when a mathematical model’s predictions leave a consequential feature of the available observations unexplained, or when a proposed use makes such a discrepancy worth examining. A model may reproduce an overall average while missing conditional responses, bursts, extremes or the records that a selection rule actually permits.

Start with one needed prediction and a feature whose failure would change its use. For overload, compare relevant tails or sequences, not only the fitted mean. Construct that feature under the model on comparable records. The first result can be a localized discrepancy, a repaired calculation, or a sufficient reason to retain a narrower use.

The principal result is a changed model, the assumption changed, and the consequence that must be recalculated. A supported restriction of use or an unresolved choice between repairs can also be the useful result. A small residual is not a certificate of adequacy; a nonzero residual is not automatically a model failure.

This is model criticism within mathematical modeling. MMP.7 supplies the recording law, MMP.11 the available model family, and MMP.13 inference within a stated model. Here the work constructs and interprets comparisons that can change that model. A physical, biological, economic or other subject method supplies the meaning and admissibility of the proposed repair. Predictive improvement alone identifies neither a causal mechanism nor an intervention effect.

Do not reopen an adequate application merely to run a standard collection of diagnostics. An established calculation, bound or checked prediction may already suffice under unchanged conditions. C.11.DUA selects further checking when its possible outcomes can change the answer, claim or warranted use. New observations, model enlargement and simulation are not routine prerequisites.