The short answer
You analyze highly verified, accurate data. You absolutely do not invent data to cover up massive engineering failures. When an Engineering Lead casually asks you to guess checkout conversion rates from raw, unstructured database tables simply because they forgot to add the telemetry tags, they are aggressively outsourcing their own incompetence. Refuse the estimation immediately and totally. State that extracting accurate, meaningful conversion funnels requires proper tracking instrumentation entirely on the front end. Tell them clearly that backend transaction tables completely lack session continuity and vital user behavior context. Demand that they immediately halt the rollout and implement the required event tags retroactively. Do not become their analytical safety net. Force them to write the missing code.
Why this question is a trap
The Engineering Lead desperately wants to close their sprint ticket and mark the epic as complete. They blindly shipped the feature and slowly realized they cannot mathematically measure its success. They want your estimation to serve as official, stamped validation for their sloppy release. They want you to provide the cover.
If you provide a rough estimation based on fragmented database logs, you permanently own the resulting metric. When the estimation is inevitably proven wrong next month, engineering will absolutely not take the blame for forgetting the tags. They will blame your incredibly poor analytical skills. You validate their highly careless release process by acting as a manual, unpaid workaround. Your job is not to clean up after lazy deployments. Your job is to strictly enforce data integrity across the company. If you estimate this critical metric once, they will stop adding telemetry tags entirely because they know you will do the heavy lifting for them in SQL. You must stop this toxic behavior immediately.
What most people say
Most Data Analysts try to be overly collaborative and highly accommodating. They desperately want to prove they are highly technical problem solvers who can overcome any obstacle.
They spend four agonizing hours writing a massive, incredibly complex SQL query trying to stitch together raw payment table timestamps just to guess at user sessions. They proudly present a wildly inaccurate, highly fragile funnel to the Engineering Lead with a dozen desperate caveats about data quality. The Engineering Lead completely ignores all the caveats, takes the final glowing percentage, and reports proudly to executive leadership that the new checkout is a massive success. The Analyst is left holding the bag completely when the actual revenue numbers do not match the falsely reported conversion rate. They ruin their own reputation to save an engineer five minutes of coding.
What to say instead
Stop writing complex SQL immediately. Stand firm on rigid architectural requirements. You are an analyst, not an alchemist.
Inform the Engineering Lead flatly that backend transaction tables absolutely do not capture drop-off intent, session bounces, or critical UI interactions. State that estimating funnel conversion without actual frontend telemetry is statistically invalid and entirely irresponsible. Tell them directly that you will absolutely not produce a metric until proper tracking instrumentation is deployed to the production environment. Advise them coldly to log a fast-follow ticket to add the explicitly missing tags today so you can begin collecting actual, measurable data tomorrow. Make their missing code their immediate problem.
The phrase to anchor on
The exact phrase to fiercely leverage is tracking instrumentation.
This precise terminology forcefully drags the conversation back to engineering fundamentals. You are not stubbornly refusing to do basic math. You are stating a cold, unyielding fact that the required tracking instrumentation does not exist. It shifts the burden of work entirely back onto their shoulders where it belongs. They cannot logically argue with the hard fact that they completely failed to instrument their own code. The phrase stops all negotiation.
How to deliver it
Deliver the strict boundary with absolute technical finality. Do not sound apologetic that you cannot perform a technical miracle. Do not sigh heavily.
Use a flat, highly declarative tone. When they inevitably argue that it is "just a quick estimation for leadership," do not debate the semantic definition of an estimate. Repeat the rigid requirement for tracking instrumentation. Hold your ground completely. If communicating over Slack, keep your response strictly under three sentences. Do not write a long, defensive paragraph explaining the technical difference between backend logs and frontend events. State the missing requirement plainly. State the specific action they must take. Stop typing immediately.
Mistakes that cost you the room
The most damaging mistake is nervously offering a "highly directional" guess just to keep them happy and get them out of your queue. A directional guess immediately becomes a factual, historical baseline in the minds of executives. Never, ever provide a number you cannot mathematically defend in an audit.
Another critical error is eagerly offering to go into the codebase and add the tags yourself to speed things up. You are an analyst, not a frontend engineer. Do not blur your role to save their sprint velocity. Let them feel the intense pain of their own missed requirement. Do not enable their bad habits.
Practice plan
This drill aggressively prepares you to hold the line against dangerous engineering shortcuts. Record yourself stating the firm refusal to estimate the metric on camera.
Ensure your voice stays totally level and does not pitch up defensively at the end of the sentence. Practice delivering the exact phrase tracking instrumentation with absolute, unwavering confidence. Rehearse the heavy silence that must follow your demand for a fast-follow ticket. Drill this highly common scenario until you are entirely comfortable letting an engineering team deal with the harsh consequences of their own missing code. Please remember this detailed guide is a rehearsal mechanism for communication scenarios. Talk Rightly does not offer formal HR or employment counsel.