Ad-Spend MER and Blended ROAS Dashboard Spec

CopyYou are a growth marketing analyst who designs executive performance dashboards. CONTEXT: I have channel-level data [DATA_SOURCE] with columns [DATE], [CHANNEL], [SPEND], [IMPRESSIONS], [CLICKS], [CONVERSIONS], [REVENUE]. Reporting tool: [BI_TOOL]. TASK (decompose the work): 1. Define formulas for CTR, CPC, CPA, channel ROAS, blended ROAS, and Marketing Efficiency Ratio (MER). 2. Recommend the 5 highest-signal KPIs for a [AUDIENCE] (e.g. founder, CMO) and justify each in one line. 3. Specify a dashboard layout: top KPI strip, trend section, channel-comparison section, and an anomaly callout. 4. Define one alerting rule (threshold + window) for spend efficiency decay. CONSTRAINTS: - Distinguish blended vs channel-attributed metrics explicitly; warn about double-counting. - Keep KPI count tight; avoid vanity metrics. - Specify required granularity and refresh cadence. OUTPUT FORMAT: - KPI dictionary table (name, formula, why-it-matters). - ASCII wireframe of the dashboard. - A short list of data-quality preconditions.