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Guardian Life Data Scientist Interview Questions & Guide 2026

Timed data scientist practice for Guardian Life: short SQL and probability sets run end to end, then scored against a rubric.

The 60-second brief

As a Data Scientist at Guardian Life, you will play a pivotal role in the company's ambitious digital transformation journey. Guardian Life is modernizing its traditional insurance operations by embedding advanced artificial intelligence and machine learning directly into its business workflows. This position is not just about building models in isolation; it is about deploying intelligent solutions that directly impact customer wellbeing, optimize underwriting processes, and streamline complex claims processing.

The boundary with engineering varies enough to be worth asking about directly. Some seats end at the analysis and the writeup; others carry feature pipelines, scheduling and alerting, which decides whether production data plumbing belongs in your prep at all.

Focus areas

  • Separate authorization, settlement and dispute outcomes cleanly
  • Report only matured cohorts for loss metrics
  • Read vintage curves, not blended portfolio averages

Overview

The work you do will directly influence how Guardian Life interacts with millions of customers. By analyzing structured and semi-structured data—such as claims histories, underwriting notes, and customer communication records—you will build predictive models that automate decision-making and enhance operational efficiency. This role sits within the Ai Studio, a highly collaborative hub where data scientists, engineers, and product owners work together to translate theoretical machine learning into production-ready software.

This position offers a unique blend of scale and innovation. You will have the opportunity to work with massive, complex datasets unique to the insurance and financial services industry. To succeed, you must possess not only strong technical capabilities in statistical modeling and programming but also the business acumen to explain your models' decisions to non-technical stakeholders, including legal and underwriting executives.

The Guardian Life interview process

Guardian Life candidates report 4 rounds · ≈ 3-5 weeks. The stages below are what candidates describe, not a published process.

Automated Screening

Rounds outside the standard loop often open with something deliberately under-specified: a loose business problem, an open question about a product area, a dataset described in one sentence. The common failure is surveying, listing six plausible approaches and committing to none of them. The thing that separates a strong answer is scoping out loud. State what you are treating as the goal, name the metric you would move, say what you are choosing not to do and why, then take one path through to an actual answer. An interviewer can follow you down a narrow path. Nobody can grade a menu.

What to demonstrate

  • Whether you turn an ambiguous prompt into a stated question with a measurable outcome before doing any work
  • The judgement visible in what you cut, and whether you say why you cut it rather than silently dropping it
  • Whether you land on a concrete recommendation with its caveat attached, rather than an unranked set of options

How to prepare

  • Take three vague prompts, such as 'is this feature working', 'why did retention drop', and 'should we expand into a new segment'. For each, write one sentence of goal, one primary metric with its window, and two things you are explicitly not doing.
  • Practise giving the recommendation first and the reasoning second, in five minutes. Loosely defined rounds are usually time-boxed, and an answer that arrives last often does not arrive.
  • Keep a running assumption list as you talk, on paper or in the shared doc, so the interviewer can challenge one assumption instead of your whole answer.

Recruiter Screen

Data Scientist covers at least four different jobs: experimentation, product analytics, causal work on observational data, and applied modelling that ships into a system. A screening call is the cheapest place to find out which of them is being hired for, and doing that diagnosis openly reads as senior rather than fussy. Ask what the last few pieces of work on the team actually were, and roughly how a week splits between querying, modelling and stakeholder time. Then say which parts of that you have done and which you have not. Claiming the whole range is the fastest way to be caught one round later.

What to demonstrate

  • Whether you can distinguish the flavours of the role and locate your own experience inside one of them honestly
  • Whether you name what you have not done instead of stretching to cover every line of the posting
  • Whether your hard constraints (notice period, location, work authorisation, level) surface now rather than at offer stage

How to prepare

  • Map the last two years of your time into rough percentages across query writing, experiment design, modelling and stakeholder work, so a question about scope has a real answer
  • Mark every responsibility in the posting as done, adjacent or new, and prepare one sentence for each adjacent item naming the closest thing you have actually built
  • Decide which logistics are non-negotiable before the call so you can state them in one sentence rather than negotiating live

Technical Evaluation

A handful of shapes account for most of what gets asked in this format: a ranking or deduplication inside groups, a running or rolling total, a period-over-period comparison, and a cohort tracked forward over time. Recognising the shape quickly is most of the speed here; deriving it from scratch while a clock runs is where the time goes. Know that a window function keeps every row while a GROUP BY collapses them, and know which one the question needs. If the exercise is in Python instead of SQL, the same shapes arrive as groupby with transform, shift and merge, and the same grain mistakes are available.

What to demonstrate

  • Whether you reach the right construct without a detour, such as ROW_NUMBER over a partition to deduplicate instead of a self-join against a MAX subquery
  • Whether you know what your window frame actually is, since adding ORDER BY inside OVER changes the default frame and silently changes a running total
  • Whether the thing runs. A near-miss that throws an error scores below a plainer query that returns the right rows.

How to prepare

  • Write each of the four shapes once from memory against a small schema and keep the working version somewhere you will reread it: dedupe with ROW_NUMBER, a running total, a month-over-month change with LAG, and a retention table
  • Compute one running total twice on data with tied timestamps, once on the default frame and once with ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW, and look at where the two disagree
  • If Python is on the table, rebuild the dedupe and the running total with groupby and cumsum, then assert the two implementations return identical rows

Deep-Dive Discussions

An added round often puts you in front of someone outside the core hiring team: a partner engineer, a product owner, a domain expert, sometimes a more senior manager. The question they are really asking is not whether you can do the work but whether they would trust a number that came from you. That changes what a good answer looks like. Lead with what the decision cost and what it changed, keep the method available but not central, and be plain about the limits of your evidence. Overstating a result is the fastest way to lose this round.

What to demonstrate

  • Whether you can explain a technical choice to someone who will never read your code, without either flattening it into nothing or hiding inside jargon
  • Honesty about evidence strength: what the analysis establishes, what it only suggests, and what it cannot say at all
  • How you take disagreement, specifically whether you update on a good objection, hold your position with reasons, or fold on contact

How to prepare

  • Write the two-sentence version of your most technical project for a non-specialist, then check that neither sentence needs a method name to make sense.
  • For one result you are proud of, write the strongest objection someone could raise and a response that concedes the part of it that is correct.
  • Prepare one decision that turned out to be wrong: how you found out, what it cost, and what you changed afterwards. A senior cross-functional interviewer asks for this more often than a technical one does.

Where candidates lose points

Counting authorizations instead of weighting them, and summing amounts across currencies

Declines skew toward high-value, cross-border and card-not-present transactions, so an unweighted approval rate can sit flat while approved value falls. Merchant retry logic also turns one declined purchase into several rows, inflating the denominator by an amount that varies by merchant and by decline reason. Amounts are held in the minor unit of the transaction currency and that unit is not always two decimals, since some currencies have none and some have three, so summing amount_minor across currencies produces a figure with no interpretation at all.

Recalibrating an underwriting cutoff on approved and funded applicants only

Rejected applicants have no repayment outcome, and they were rejected because the incumbent model scored them badly, so the missingness depends directly on the outcome being modelled. Reject inference by augmentation or parcelling fills the gap using the incumbent model's own assumptions, which means it can confirm those assumptions but cannot test them. The only genuinely new information about the reject region comes from bureau performance on rejects who borrowed elsewhere, or from a deliberately randomised approval band around the cutoff.

Averaging per-user rates to produce a population rate

Decide which quantity you want: the mean of per-user ratios and the ratio of summed numerator to summed denominator are different estimands, and heavy users dominate one but not the other. For a ratio metric, aggregate numerator and denominator separately and use the delta method for its variance.

Building features from data that postdates the prediction time

Check every feature against the timestamp at which the model would actually score, and drop anything computed from a window that includes or follows the label event. For a forecasting use case, split train and test by time rather than at random, and split by entity when the same entity recurs.

Questions & practice

How do you approach model governance and documentation to ensure your algorithms comply with internal risk standards?

Medium · machine learning and modelling

Approach

  1. Say how the offline result would be validated online before it is trusted.
  2. Frame the prediction: the label, the moment of prediction, and the action it triggers.
  3. Pick an evaluation metric that matches the cost of each error type, not a default.

Follow-up

  • What would you monitor after launch to know the model is still valid?
  • How would you choose the decision threshold, and who owns that choice?

Explain the mathematical difference between Random Forest and XGBoost, and describe a scenario where you would prefer one over the other.

Medium · machine learning and modelling

Approach

  1. Frame the prediction: the label, the moment of prediction, and the action it triggers.
  2. Set a baseline first, so any model has something honest to beat.
  3. Check what information would not exist at prediction time, and exclude it.

Follow-up

  • Where could label leakage enter this setup?
  • What would you monitor after launch to know the model is still valid?

Estimate a delinquency roll-rate matrix and project twelve months

Hard · roll rates · markov chain · survivorship

fct_loan_performance_monthly gives loan_id, as_of_month_end, months_on_book, delinquency_bucket, charge_off_flag, prepaid_in_full_flag and restructured_flag. Build a month-to-month transition matrix over the five delinquency buckets plus absorbing charged_off and prepaid states. Loans that stop appearing must be routed to an absorbing state rather than dropped. Project the current book forward 12 months by repeated matrix multiplication and report the projected share reaching charge-off. Handle restructured_flag explicitly, and name one place the Markov assumption fails on this data.

Approach

  1. Build consecutive month pairs per loan by shifting as_of_month_end within loan_id, then verify the shifted value is exactly one month later. A gap is not a transition, it is an exit you have not resolved yet.
  2. Resolve exits before counting anything. A loan whose last row carries charge_off_flag moves to charged_off, one carrying prepaid_in_full_flag moves to prepaid, and one that disappears with neither is a data question to raise rather than silently discard, because discarding it is survivorship that inflates every cure rate.
  3. Count pairs into a 7 by 7 matrix and row-normalise. Assert every row sums to one and the two absorbing rows are the identity; a row that does not sum to one means exits were dropped.
  4. Decide and state the restructure rule. Restructuring resets days_past_due, so a dpd_60_89 to current move on a restructured loan is not a cure. Either give restructured loans their own state or carry the pre-restructure bucket, but do not let that move land in the cure cell.
  5. Project by taking the current bucket distribution as a row vector and multiplying by the matrix twelve times. Report the charged_off entry, and report it again from an all-current starting vector so the reader can see how much of the projection comes from loans that are already delinquent today.
  6. State the homogeneity failure plainly: transition rates depend strongly on months_on_book, so one pooled matrix applied to a book with a young mix understates early-life delinquency. If the mix is moving, estimate separate matrices by seasoning band.

Worked solution (45 min)

  1. Sort by loan_id and as_of_month_end, shift to form (from_state, to_state) pairs, and flag pairs whose month gap is not exactly one.
  2. For each loan's final row, assign the absorbing destination from charge_off_flag or prepaid_in_full_flag, and list loans that vanish with neither as an exception count to report.
  3. Apply the restructure rule, then build the 7 by 7 count matrix with a cross-tabulation over ordered state categories and row-normalise it.
  4. Assert row sums equal one and absorbing rows are the identity, then take the current month's bucket distribution as a row vector.
  5. Multiply twelve times, report the charged_off component, and repeat from an all-current vector for comparison.

Expected result: A 7 by 7 row-stochastic matrix with identity rows for charged_off and prepaid, a current-to-current diagonal typically above 0.95, roll rates rising with bucket depth, and a 12-month projected charge-off share of a few percentage points from an all-current start and materially higher from the actual book.

Verify it yourself

  • Every row sums to one within floating-point tolerance, and both absorbing rows are exactly the identity.
  • No mass sits in cells that skip a bucket upward, such as dpd_1_29 to dpd_60_89 in one month; if there is, the pairs are not actually consecutive months.
  • The projection from an all-current start is strictly below the projection from the real book distribution.
  • Backtest by estimating on months up to t minus 12 and comparing the projected distribution with the realised one at t; a systematic optimistic gap points at dropped exits or at seasoning, not at noise.

Follow-up

  • How would you validate the projection against what actually happened, and over what window?
  • The cure rate out of dpd_30_59 rose five points last quarter. What are the candidate explanations and how would you separate them?
  • When would you prefer a vintage curve to a roll-rate projection, and why?

Explain how memory management works in Python, and describe the difference between a list and a generator.

Medium · sql and data manipulation

Approach

  1. Say which table is the grain you start from, and join outward from it.
  2. Check whether any join is one-to-many before aggregating, or the sums inflate.
  3. Handle the rows that do not match: a LEFT JOIN with a NULL check is usually the question.

Follow-up

  • How does the query change if the join becomes one-to-many?
  • How would you verify this result without re-running the same query?

What is your typical workflow for version control when collaborating with multiple data scientists on a single code repository?

Medium · sql and data manipulation

Approach

  1. Compute rates by summing numerator and denominator separately, never by averaging rates.
  2. Say which table is the grain you start from, and join outward from it.
  3. Handle the rows that do not match: a LEFT JOIN with a NULL check is usually the question.

Follow-up

  • How does the query change if the join becomes one-to-many?
  • How would you verify this result without re-running the same query?

Write a Python script using pandas to clean a raw dataset containing missing values and inconsistent date formats.

Medium · sql and data manipulation

Approach

  1. Compute rates by summing numerator and denominator separately, never by averaging rates.
  2. Say which table is the grain you start from, and join outward from it.
  3. Handle the rows that do not match: a LEFT JOIN with a NULL check is usually the question.

Follow-up

  • How would you verify this result without re-running the same query?
  • What breaks if events arrive late or out of order?

Explain the difference between deep copying and shallow copying in Python.

Medium · sql and data manipulation

Approach

  1. Check whether any join is one-to-many before aggregating, or the sums inflate.
  2. Compute rates by summing numerator and denominator separately, never by averaging rates.
  3. Say which table is the grain you start from, and join outward from it.

Follow-up

  • What breaks if events arrive late or out of order?
  • How would you verify this result without re-running the same query?

Count-weighted and dollar-weighted approval rates on one currency

Easy · aggregation · denominators · minor units

Using fct_payment_authorization, report the trailing 7-day authorization approval rate two ways for transaction_currency = 'EUR': count-weighted, and dollar-weighted on amount_minor. Exclude is_reversal = true, exclude incremental authorizations (parent_auth_id not null), and exclude zero-amount account verifications. auth_result = 'approved' is the numerator; the four declined_* values make up the rest of the denominator. Return channel, attempts, approved_attempts, approval_rate_count and approval_rate_value. State every exclusion and its reason before you write the SELECT.

Approach

  1. Say the denominator out loud first: attempts on a single transaction currency, excluding reversals, incremental authorizations and zero-amount verifications, because none of those is a purchase attempt a merchant is trying to get approved.
  2. Filter requested_at against a half-open interval (>= start AND < end) so the boundary day is neither dropped nor double counted.
  3. Compute both rates in one pass with FILTER clauses: COUNT() FILTER (WHERE auth_result = 'approved') over COUNT(), and SUM(amount_minor) FILTER (WHERE auth_result = 'approved') over SUM(amount_minor).
  4. Cast one side of each ratio to numeric before dividing, since amount_minor and the counts are integers and integer division silently truncates to zero.
  5. Group by channel and sort by the value-weighted rate, then read the gap between the two rates as a statement about where the declines sit rather than as noise.

Worked solution (20 min)

  1. Write the exclusion list as comments above the query: is_reversal = false, parent_auth_id is null, amount_minor > 0, transaction_currency = 'EUR'.
  2. Build a single aggregate query over fct_payment_authorization with a half-open requested_at predicate and those four filters.
  3. Emit attempts, approved_attempts, approval_rate_count and approval_rate_value with FILTER clauses and a numeric cast on the numerator.
  4. Group by channel, order by approval_rate_value ascending so the worst channel is on top.

Expected result: One row per channel present in the window, with attempts and approved_attempts as integers and both rates as numerics strictly between 0 and 1. approval_rate_value is typically lower than approval_rate_count on ecommerce and moto, because declines concentrate in higher-value card-not-present traffic.

Verify it yourself

  • SUM(attempts) across channels equals a separate COUNT(*) run with the same four filters and no GROUP BY.
  • Dropping the amount_minor > 0 filter raises attempts and moves approval_rate_count while leaving approval_rate_value unchanged, which confirms the zero-amount rows were only ever affecting the count-weighted figure.
  • Both rates are strictly less than 1 unless a channel had no declines at all in the window.

Follow-up

  • The two rates diverge by four points on the ecommerce channel but agree on card_present. What does that tell you, and what would you cut next?
  • How would you extend this to all currencies without summing amount_minor across them?
  • Which of the four decline reasons belong in the denominator of a rate you would put in front of a risk team, and which are really the network's problem?

Describe how you would design a system to automatically extract key entities from semi-structured customer emails.

Medium

Approach

  1. Say what you would check first and why it is the highest-information step.
  2. State your assumptions explicitly before working the problem.
  3. Work from the decision backwards to the evidence you would need.

Follow-up

  • How would you know your answer was wrong?
  • What assumption would you test first?

Measure an underwriting automation programme without hiding cost

Medium · metric gaming · swap set · operations metrics

An operations programme aims to cut manual underwriting. The proposed metric is manual review rate: decided_by = 'manual' over applications with decision in ('approve','decline') in fct_loan_application. The team controls the referral rules recorded in policy_rule_hits. Explain how they can halve that metric in one release while making the book worse, then design the readout that catches it: primary metric, the cuts it must always be reported in, and the guardrails. Say what evidence you would require before declaring a batch of referrals safe to auto-decide.

Approach

  1. Name the exploit precisely. Referrals can be converted to automatic declines by a rule change, which removes them from the numerator at no operational cost while they stay in the denominator, so the rate falls and applicants a human would have approved are rejected instead. Auto-approving the same population moves the metric identically with the mirror-image failure mode.
  2. Refuse the bare rate as a primary. Make it conditional on outcomes: manual review rate measured at a held-constant approval rate within each model_pd_12m band, so a reduction is creditable only when the decisions themselves did not move.
  3. Require fixed cuts on every report: by model_pd_12m band and by the rule identifier inside policy_rule_hits. A single blended operations number cannot be decomposed after the fact, and the decomposition is the entire diagnostic.
  4. Set guardrails on the things the exploit disturbs: approval rate within each score band, the override rate where manual decisions disagree with the automated recommendation, and the vintage 90+ rate at months_on_book = 12 for the newly auto-decided population against the referrals of the prior regime.
  5. Fix the evidence bar for retiring a referral rule: a shadow period where the rule fires and the case is still worked manually, recording what the automation would have decided, what the human decided, and, for the disagreement group alone, the realised performance. Agreement on the easy majority establishes nothing about the disputed minority.
  6. State the conflict honestly rather than designing around it. The referral population exists because the model is least certain there, so automating it trades loss for cost by construction, and the readout's job is to price that trade rather than to make it disappear.

Worked solution (30 min)

  1. Compute manual review rate for a recent month overall, then by model_pd_12m band, then by rule identifier extracted from policy_rule_hits.
  2. For each rule, compute the approve share and decline share of the applications it touches, so the rules whose removal would actually change decisions are identified before anyone proposes removing them.
  3. Simulate the exploit: reclassify one high-volume referral rule's applications as automatic declines, then recompute the blended rate and the band-level approval rates side by side.
  4. Write the readout spec: the primary with its conditioning, the two mandatory cuts, the three guardrails, and the shadow-period evidence bar.

Expected result: A table in which the simulated rule change lowers the blended manual review rate materially while approval rate in the affected model_pd_12m bands falls at the same time, together with a readout spec that makes it impossible to publish the first effect without the second.

Verify it yourself

  • The simulated change lowers the manual review rate and the band-level approval rate together. If band approval rate is unchanged, that rule was not binding and its removal is genuinely free.
  • Rule-level counts reconcile to the blended rate once applications hitting several rules are counted once. A jsonb array of rule identifiers is the usual place this double-counts.
  • The newly auto-decided population and the prior manual referrals are compared at equal months on book, not at equal calendar dates.

Follow-up

  • The override rate falls to near zero after the change. Is that good?
  • How long must the shadow period run, given the outcome matures at twelve months on book?
  • The rule fires on 200 applications a month. What can and cannot be established at that volume?

Approval rate rose in every band yet fell overall

Medium · mix shift · simpsons paradox · segmentation

Monthly application approval rate on fct_loan_application fell from 62 to 57 percent. Cut by bureau_score band, the rate rose in every band, including the null-bureau band. Columns: application_id, channel, submitted_at, requested_amount_minor, declared_annual_income_minor, bureau_score, model_pd_12m, model_version, policy_rule_hits, decision, decided_by, decision_at. The denominator is decision in ('approve','decline'). Explain the arithmetic, quantify how much of the five-point fall is mix versus within-band movement, and say what you would tell the team that owns acquisition.

Approach

  1. Confirm the paradox is real rather than a banding artefact. Rebuild the bands on fixed cutpoints taken from the earlier period, because quantile bands re-cut each month move with the population and can manufacture this pattern on their own.
  2. Compute the exact decomposition rather than describing it: within = sum of w_i0 * (r_i1 - r_i0), mix = sum of r_i0 * (w_i1 - w_i0), interaction = sum of (w_i1 - w_i0) * (r_i1 - r_i0). The three terms sum identically to the change in the blended rate, so the report can state the split.
  3. Attribute the weight change by cutting the same fixed bands by channel. Keep null bureau_score as its own band; a thin file is a population signal, not missing data to be imputed away.
  4. Check whether the new arrivals also changed the population inside a band, by comparing requested_amount_minor and declared_annual_income_minor distributions within one band across the two months.
  5. Deliver two numbers rather than one story: policy is looser in every band, and the funnel is being fed a different population. Those have different owners and different fixes.

Follow-up

  • If the new channel is profitable at its own approval rate, is the blended fall a problem at all?
  • How would you present this so that nobody reads the blended series unaccompanied again?
  • What breaks if you fix the mix by reweighting to a frozen band distribution every month?

Suggested practice checklist

For someone who can already write the query and train the model but stalls when asked what to measure or whether a change is worth making. Metric definition and case structure come first; the technical work is kept as maintenance rather than the centre of the week.

Day 1 — Metric anatomy

  • For three products you use daily, write one primary metric, two input metrics that plausibly move it, and one guardrail that would catch a cheap way of moving the primary at the cost of the product.
  • For one of them, specify the metric precisely enough that two analysts would return the same number: numerator, denominator, unit of observation, time window, and how returning and deleted accounts are treated.
  • Pick a ratio metric and write what happens to it when the denominator shrinks for reasons unrelated to the numerator, with a concrete example of that happening.

Deliverable: A one-page metric tree for one product, with the primary metric written as an unambiguous spec.

Day 2 — Diagnosing a drop without guessing

  • Take the prompt "weekly active users fell 8 percent week over week" and write the segmentation plan before proposing any cause: platform, region, tenure cohort, acquisition channel, and whether the movement sits in the numerator or in a changed denominator.
  • List the instrumentation failures that manufacture fake drops (a client release that stopped firing an event, a bot filter change, a shifted date boundary or timezone) and write the query that rules out each one.
  • Rehearse stating the boring explanations first, seasonality and day-of-week composition, before reaching for a product cause.

Deliverable: A drop-diagnosis checklist short enough to recite from memory in under a minute.

Day 3 — Should we build it

  • Take a feature idea and write it as a bet: what you believe is true, what would have to be true for it to pay off, the metric that would confirm it, and the effect size that would justify the engineering cost.
  • Size the opportunity top-down and bottom-up, then reconcile the two numbers in writing instead of quoting whichever is friendlier.
  • Write the counter-metric that would make you kill the feature even if it wins on the primary metric.

Deliverable: A one-page product memo ending in a decision rather than a list of considerations.

Day 4 — The places aggregate numbers lie

  • Construct a Simpson's paradox numerically: two segments where the treatment wins within each segment yet loses overall, and identify the shift in segment weights that causes it.
  • Take a heavy right-tailed quantity such as revenue per user and write why the mean is the wrong summary, which percentile you would report instead, and what a moving mean with a stable median tells you.
  • Write your definition of a session for the product from day one, then name two real behaviours it misclassifies.

Deliverable: One page holding a worked Simpson's paradox table and a session definition with its two known failure cases.

Day 5 — Technical maintenance, aimed at metrics

  • Solve four timed SQL prompts that all end in a ratio metric, so the question of grain stays live in every answer.
  • Compute a 95 percent confidence interval for a proportion on a small sample, and state why the normal approximation is unreliable when either np or n(1 minus p) falls below roughly 10, along with which interval you would use instead.
  • Take one metric from your day-one tree, write the query that computes it correctly, then write the query that computes it wrong in the most plausible way and explain how you would notice.

Deliverable: Four solved prompts plus a matched correct and plausible-wrong query for one metric.

Day 6 — Turning engineering work into data science stories

  • Write three project stories as situation, decision, trade-off, outcome, each carrying one number and one thing you got wrong.
  • For the story you will lead with, prepare an answer to "what would you do differently" that names a decision you made, not a constraint you were handed.
  • Practise the sentence that reframes a systems project as a question project: the question the work answered, ahead of the pipeline it shipped.

Deliverable: Three written stories with the lead story delivered aloud and timed under four minutes.

Day 7 — Mock case and gap list

  • Run a 40-minute mock case with someone playing a product manager who pushes back on your metric choice, and record it.
  • Listen back and mark every moment you proposed a solution before the success metric existed.
  • Rewrite those moments as the question you should have asked, and rehearse the first 90 seconds of the case until scoping comes before solving.

Deliverable: A recorded case plus a rewritten opening 90 seconds.

Your part, not the team's

Most data work is done by groups, so an interviewer has to work out which piece was yours. An answer that runs on 'we' for several minutes gets interrupted with a question about what you personally did, and by then the answer sounds defensive even when it is true. Mark your own contribution as you go, and name the parts that belonged to someone else instead of leaving them ambiguous. Keep a few specifics back as well, like the name of the metric or who actually objected, so a probe can be answered with something you had not already said.

How do you handle domain-specific jargon or abbreviations when building an NLP pipeline for insurance documents?

Medium · behavioural and stakeholder questions

Approach

  1. State the situation in two sentences and spend the rest on your reasoning.
  2. Close with what you would do differently, concretely.
  3. Name the disagreement or constraint, and how you resolved it with evidence.

Follow-up

  • How did you know the outcome was caused by your change?
  • What did you decide not to do, and why?

Explain the concept of gradient descent to a non-technical business stakeholder.

Medium · behavioural and stakeholder questions

Approach

  1. Pick a story where you drove the decision, not one where you observed it.
  2. Name the disagreement or constraint, and how you resolved it with evidence.
  3. State the situation in two sentences and spend the rest on your reasoning.

Follow-up

  • What would you do differently if you ran that project again?
  • What did you decide not to do, and why?

Allocate one analyst-week across three competing risk requests

Medium · prioritisation · decision deadlines · stakeholder negotiation

Three requests land in the same week and you have one analyst-week. Payments wants a merchant-level decline teardown before a contract renewal in nine days. Credit wants a swap-set analysis on a cutoff change scheduled to ship in six weeks. Insurance wants accident-quarter loss ratios at 12 months development for a reserving review with no fixed date. Each sponsor believes theirs is first, and each has escalated before. Produce the allocation, the reasoning you would say out loud to all three at once, and what you explicitly drop.

Approach

  1. Score each request on the decision it unblocks rather than on effort or on how loudly it arrived: what changes if it is late, and is that change reversible.
  2. Separate deadline from value. The nine-day renewal is a hard, irreversible date with a bounded prize; the six-week cutoff has slack but a much larger downside if it ships unmeasured; the reserving number has no date but feeds external reporting, which is its own kind of hard.
  3. Hunt for the cheap partial in each: a decline teardown restricted to the top merchants by declined value usually answers the contract question at a fraction of the full cut.
  4. Sequence by hard date first, then by largest irreversible downside, and deliver the trade-off to all three sponsors in one message rather than three, so nobody negotiates privately against a version you told someone else.
  5. Name what is dropped and who now owns that consequence, in writing, so the trade-off is visible rather than silently absorbed by you.

Follow-up

  • The credit sponsor escalates to your manager. What do you change, and what do you refuse to change?
  • How would you make this allocation reproducible so the next contested week is a rule application rather than a negotiation?