EAM.13:11 - SoTA-Echoing

For deciding whether new observations require an asset-plan revision, select a matched comparison of the actual outcome with the premise used in the decision, followed by reconsideration of the affected future option. Adopt C.16’s comparison-basis discipline and C.11.DUA’s connection between an inquiry and the decision it can improve. The Solution therefore separates the observed variance, an explanation of that variance and the next choice. In the expenditure example, the applicable bills permit a price-premise update while service performance remains a separate question. This yields a usable current answer without waiting for a general explanation of the intervention’s effectiveness.

A serious alternative when the receiving question concerns attributable effects is an experimental or quasi-experimental impact evaluation. The Magenta Book: Central Government guidance on evaluation, updated 15 May 2026, chapter 2, “Experimental and quasi-experimental approaches to impact evaluation”, supplies that comparator: comparison with a defensible unaffected group or period, supported by adequate data. Adapt such a design when the causal answer could change continuation or replication and the comparison can be obtained. For the present cost-premise update, its additional design, data and elapsed-time demands would buy a stronger claim than the decision needs. The selected narrower answer accepts unresolved causal attribution; it is not a lower-cost way to establish the same causal effect. The guide also allows other impact-evaluation approaches where a credible counterfactual is unavailable, so no universal control-group requirement follows. Reopen the choice when a repeat-investment decision depends on the intervention’s effect, unexplained changes reverse the supported plan, or newly available comparison evidence makes a consequential causal inquiry worthwhile. The source’s government evaluation context supplies no observed CityWater outcome.