Seagen · Data Scientist
Updated · 2026-09-24

Seagen Data Scientist
Interview Questions & Guide 2026

THE 60-SECOND BRIEF

A Data Scientist at Seagen operates at the critical intersection of advanced analytics, biostatistics, and oncology research. In this role, you are not merely building models; you are translating complex clinical and genomic data into actionable insights that directly influence the development of life-saving antibody-drug conjugates and other therapeutic innovations. Your work serves as the backbone for evidence-based decision-making, impacting everything from clinical trial design to the optimization of patient outcomes.

Allocate prep to your weakest link rather than your favourite topic. Of the three things that usually gate the outcome (SQL that is correct under messy joins, sound reasoning about experiments, and structured framing of an open-ended problem), candidates tend to over-invest in modelling theory and under-invest in framing.

PracHub has no confirmed round sequence for Seagen. Treat the sections below as preparation areas and confirm the format with your recruiter.

Correct for claims runout before reporting recent monthsSeparate censoring from events in time-to-event modelsMinimise protected health information in every extract

29 min read

Browse Data Scientist questions

See the practice prompts

13Practice promptsAcross five skill areas
3With worked solutionsIncluded in the practice prompts

A Data Scientist at Seagen operates at the critical intersection of advanced analytics, biostatistics, and oncology research. In this role, you are not merely building models; you are translating complex clinical and genomic data into actionable insights that directly influence the development of life-saving antibody-drug conjugates and other therapeutic innovations. Your work serves as the backbone for evidence-based decision-making, impacting everything from clinical trial design to the optimization of patient outcomes.

You will find yourself collaborating with a multidisciplinary ecosystem of biostatisticians, medical directors, and software engineers. The environment is highly rigorous, reflecting the high stakes of the pharmaceutical industry. Success here requires the ability to distill complex technical findings into clear, persuasive narratives for non-technical stakeholders, ensuring that data-driven insights are fully integrated into the drug development pipeline.

Seagen prioritizes candidates who can demonstrate not just technical proficiency, but a genuine passion for the mission of transforming cancer care through precision medicine.

01

Preparation focus

editorial

No round sequence has been reported for this company, so work the categories below and confirm the format with your recruiter.

What to demonstrate

  • Breadth across SQL, experimentation and product reasoning
  • Ability to state assumptions before choosing a method

How to prepare

  • Drill the practice exercises below and time yourself
  • Prepare three quantified stories about decisions you drove
PracHub interview preparation framework ↗

PracHub editorial advice for the preparation topics above.

01

Immortal time in adherence, treatment, and enrolment definitions

Classifying members as adherent, treated, or programme-enrolled requires them to survive and stay covered long enough to accumulate the defining events. That guaranteed event-free interval is assigned to the exposed group, so the exposure looks protective for reasons that have nothing to do with the treatment. Adherence studies are the classic case: measuring 12-month proportion of days covered and then comparing mortality builds survival into the exposure definition. Use time-varying exposure or a landmark analysis with the classification window excluded from follow-up.

02

Treating clinical measurements as missing at random

A lab result, a vital sign, or a screening exists because someone ordered it, and ordering tracks suspicion of disease, visit frequency, and site workflow. Imputing the mean or dropping incomplete rows biases the population estimate and can flip the sign of an association, because the untested are systematically healthier or systematically disengaged. The presence indicator is often more predictive than the value, which is a warning sign rather than a feature win: a model that learns test ordering will not transfer to a site with different protocols.

03

Crediting a treatment for regression to the mean

Selecting a group because it is extreme (lowest-engagement users, accounts having their worst month, the bottom decile of a score) moves that group's expected next-period value back toward the average even under no treatment, by exactly as much as the selecting measure is imperfectly correlated with its own later value. Compare against units that met the same selection rule and went untreated, or use two pre-periods so the bounce-back is visible before the intervention starts. A pre-post number on a group chosen for being extreme measures the selection rule, not the treatment.

04

Optimising accuracy on a heavily imbalanced target

State the base rate first, then choose the metric from the relative cost of a false positive against a false negative: precision and recall at the operating threshold, PR-AUC, or expected cost. At a 1 percent positive rate, predicting the majority class for everyone scores 99 percent accuracy and is worthless.

Choose a category, try a prompt, then open its approach, worked solution or follow-up when you need it.

10 technical prompts3 include a worked solution

Given a specific clinical dataset, which machine learning model would …

medium
machine learning and modelling

Given a specific clinical dataset, which machine learning model would you choose to implement and why?

Approach
  1. Say how the offline result would be validated online before it is trusted.
  2. Set a baseline first, so any model has something honest to beat.
  3. Frame the prediction: the label, the moment of prediction, and the action it triggers.
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?

Collapse claim versions before summing allowed amounts by member

easyWorked solution
claim versioninggroupbydeduplication

You are given medical_claim_line as a pandas DataFrame: claim_line_id, claim_id, claim_version, frequency_code (1 original, 7 replacement, 8 void), member_id, service_start_date, procedure_code, allowed_amount, claim_status. Return total allowed_amount per member for service dates in one stated calendar month, counting each claim once at its surviving version and excluding any claim whose surviving version is a void. Multi-line claims must keep every line of that surviving version. Output columns: member_id, allowed_amount, sorted descending. Do not deduplicate on claim_id alone.

Approach
  1. Separate the two grains out loud before writing code: versions live at the claim level, dollars live at the line level. Every bug in this exercise comes from mixing them.
  2. Compute the surviving version per claim with a groupby transform of max over claim_version, then keep the lines whose claim_version equals that value. A transform keeps the frame at line grain, which a sort plus head(1) does not.
  3. Drop whole claims whose surviving version carries frequency_code 8. A void is not a zero-dollar line, it retracts the claim, so filtering rows rather than claims leaves the prior version's lines behind.
  4. Filter to claim_status 'paid' and state the assumption: denied, pended and reversed lines carry an allowed_amount that never became a liability, so including them overstates cost.
  5. Restrict service_start_date to the month boundaries, then groupby member_id and sum. Sort descending and return.
Worked solution 20 min
  1. Build a max-version lookup per claim_id with groupby('claim_id')['claim_version'].transform('max') and keep rows where claim_version equals it.
  2. From the surviving rows, collect the claim_ids whose frequency_code is 8 and drop those claim_ids entirely.
  3. Filter claim_status to 'paid' and service_start_date into the month window.
  4. Group by member_id, sum allowed_amount, sort descending, reset the index.
EXPECTED RESULTA two-column frame member_id, allowed_amount. On a claim with versions 1, 7, 7 only the third version's lines contribute; a claim whose latest version is frequency_code 8 appears nowhere. Total allowed is strictly below a naive sum over all rows whenever any claim in the sample was adjusted, and equal to it when none was.
Follow-up
  • A claim has versions 1, 7, 7 where the second replacement has fewer lines than the first. What does your code return and is that correct?
  • How would you handle a claim whose lines span two calendar months at the boundary of the reporting window?
  • The same logic has to run over 400 million lines in a warehouse. What changes, and what stays the same?

Simulate how ignoring clustering inflates the false positive rate

medium
simulationdesign effecttype i error

Simulate a provider-level comparison with no true effect. 40 providers, 60 members each, a continuous outcome with total variance 1 and intraclass correlation 0.02. Randomise providers 20 to 20, not members. Over 5,000 replications, report the share of replications where a two-sample t-test run on all 2,400 individual observations, ignoring provider, returns p below 0.05. Report the same share when the unit of analysis is the 40 provider means. Then state how the first number follows from the design effect 1 + (m - 1) x ICC.

Approach
  1. Decompose the variance explicitly rather than tuning it: provider variance = ICC = 0.02, residual variance = 1 - ICC = 0.98. Draw u_j once per provider and e_ij per member, so the outcome is u_j + e_ij and the correlation between two members of one provider is 0.02 by construction.
  2. Randomise at the provider level. That is the entire mechanism: the treatment indicator is constant within a provider, so in any single replicate the provider intercepts are confounded with the arm, and the naive test reads that confounding as signal.
  3. Vectorise over replications with a (reps, providers, members) array. 5,000 x 2,400 normals is trivial in numpy, and a Python loop is what tempts people to cut replications to 500 and report a number with Monte Carlo noise of plus or minus 0.017.
  4. Predict the answer before running it: design effect = 1 + (60 - 1) x 0.02 = 2.18, naive standard errors are too small by sqrt(2.18) = 1.476, so the rejection rate at nominal 0.05 is about 2 x (1 - Phi(1.96 / 1.476)) = 0.18. Agreement between prediction and simulation is what makes the result a demonstration rather than an anecdote.
  5. Run the provider-mean analysis as the control. Recovering 0.05 there proves the generator is correct and isolates the failure to the analysis unit.
Follow-up
  • How many providers would you need for 80 percent power on a 0.2 SD difference with 60 members each and this ICC?
  • Cluster sizes are unequal in reality. The design effect approximation becomes 1 + ((1 + CV^2) x mbar - 1) x ICC. Which direction does that move your sample size and why?
  • The intervention cannot be withheld from any provider. Sketch a design that still yields a defensible estimate.

Roughly 90 minutes a night on weekdays with one longer weekend block. The plan deliberately cuts scope rather than compressing everything, on the assumption that finishing one thing a night beats half-starting four.

Small steps. Visible outcomes.0 / 7 completed
ONE WEEK · YOUR PACE

Prepare, practise & reflect

One practical outcome each day. Spend longer where you need it.

0 / 7 done
01Fix the scope and set a baseline
  • Read the role description and write the three things the loop will almost certainly test, then write an explicit not-doing list for everything else and keep it visible all week.
  • Take one 20-minute SQL prompt and one 10-minute metric question cold, and write the single sentence that says what blocked each attempt, since that sentence is what decides which two topics get the most evenings.
  • Set the week's one rule: one problem finished to completion every night, including the night you only have 40 minutes.

Deliverable: A one-page scope with an explicit not-doing list and two cold attempts, each carrying one sentence on what blocked it.

Practice prompt ↗Practice prompt ↗Worked solution ↗
02One query pattern, written three times
  • Choose the single pattern most likely to appear (a cohort retention grid, or a funnel counted by user) and write it three times from a blank file rather than editing the previous attempt.
  • On the third attempt, write the grain of every CTE as a comment before writing its body.
  • Stop at 90 minutes even if the third version is imperfect, and write the one thing you would fix with another hour.

Deliverable: Three independent versions of the same query plus a note on what changed between them.

Practice prompt ↗Practice prompt ↗
03Only the statistics you will be asked to defend
  • Write, in under 200 words, how you would decide whether a difference between two groups is real: the test, its assumptions, and what you would switch to when an assumption fails.
  • Compute a 95 percent confidence interval for a difference in proportions by hand on realistic numbers, then write in one sentence what changes if the two samples are paired rather than independent.
  • Write your answer to "what does a p-value mean", check it against a definition, and delete the version that describes it as the probability the hypothesis is true.

Deliverable: A 200-word written answer and one hand-computed interval you can reproduce under pressure.

Practice prompt ↗Practice prompt ↗
04One case, and the assumptions holding it up
  • Answer one product case aloud in 20 minutes with a recording running, then listen back with a pen and mark every claim you asserted without saying what it rested on: an assumed user behaviour, an assumed data source, an assumed baseline rate, an assumed grain.
  • Pick the three assumptions the recommendation actually depends on, write how you would check each one against data, and say which one being wrong would flip the recommendation rather than merely weaken it.
  • Write the four-step structure you used onto a card small enough to hold in working memory when you are nervous.

Deliverable: One recording, three load-bearing assumptions each with a written check, and a four-step structure card.

Practice prompt ↗Practice prompt ↗Worked solution ↗
05Your own work, timed
  • Write a 90-second version and a four-minute version of your main project, and time both out loud rather than reading them.
  • Prepare answers to the two follow-ups that always come: what you would do differently, and how you knew it worked.
  • Put one number in the first sentence and be able to say exactly where that number came from and what it excludes.

Deliverable: Two timed narratives with one defensible number in the opening line.

Practice prompt ↗Practice prompt ↗
06The one full rehearsal, in a longer weekend block
  • Run a 60-minute mock covering query work, a case and a behavioural question in a single sitting with no breaks, because sustained attention is the thing evenings have not trained.
  • Immediately afterwards, and before hearing any feedback, write the three moments you lost the thread.
  • Spend the rest of the block only on those three moments, and on nothing you merely feel shaky about.

Deliverable: Mock notes naming three failure moments with a specific fix written under each.

Practice prompt ↗Practice prompt ↗
07Taper
  • Write the 20-minute warm-up you will actually do on the morning of the interview: one query you can already write from a blank file, one metric you can define out loud, and nothing you have never seen before.
  • Re-read only your own notes from this week, and open no new material.
  • Write down the logistics: the tool you will be asked to work in, whether lookups are allowed, and the sentence you will use when you do not know something.

Deliverable: A one-page card holding the case structure, the project numbers, and the logistics.

Practice prompt ↗Worked solution ↗

Expand any day for tasks and deliverables. Your progress is saved on this device.

Work that nobody used is a common and unflattering pattern in data careers, and interviewers probe for it. Have a story about an analysis that changed a decision, and be specific about how you got it in front of the person who could act. Also have one about work that went nowhere, with your reading of why.

How do you handle missing or noisy data in a clinical research context…

medium
behavioural and stakeholder questions

How do you handle missing or noisy data in a clinical research context?

Approach
  1. Name the disagreement or constraint, and how you resolved it with evidence.
  2. State the situation in two sentences and spend the rest on your reasoning.
  3. Close with what you would do differently, concretely.
Follow-up
  • What did you decide not to do, and why?
  • What would you do differently if you ran that project again?

Own an analysis that shipped wrong and was acted on

easy
retrospectiveownershipdata quality

Describe an analysis you delivered that was wrong, where someone acted on it before the error surfaced. Pick something with a mechanism you can name, not a typo. Cover what the number claimed, what was actually true, how much time passed before it was caught, who caught it, and what you told the people who had already acted. Deliverable: a five-minute account that ends with the specific control you added afterwards, plus one occasion since when that control has fired.

Approach
  1. Read the probe: the interviewer is testing whether you detect your own errors and whether the correction was structural. Pick an error with a nameable mechanism (a denominator built from distinct members instead of member-months, a series read before claims runout completed, a cohort selected on the outcome) so the story has a diagnosis rather than a mood.
  2. Open with the decision that was made on your number, not with the bug. The severity of an analytic error is measured in the action it caused: a rate filing, a staffing plan, a programme expansion.
  3. State the counterfactual number. 'The true figure was 14.1 admissions per 1,000 member-years, not 9.8' is a fact; 'it was off by a lot' is not.
  4. Describe the detection path honestly, including whether you found it or somebody else did. Say how long it took, because time to detection is the part you actually control next time.
  5. Close on the control, and make it something that protects a reader who has never met you: a unit test on the denominator, a paid-through date stamped on every chart, a required exclusions block in the spec template. Name one later date it caught something.
Follow-up
  • What would have had to be true for you to catch this before delivery rather than after?
  • Did the stakeholder change how much they trust your work, and did you want them to?
  • Give an example of a control you added that turned out to be the wrong control.

Push back on an over-broad extract without blocking the work

hard
minimum necessaryde-identificationgovernance

A researcher asks for a one-off extract covering 12,000 members: member_id, date of birth, five-digit residential postal code, full lab_result rows including value_text, and clinical note text, held on their laptop for a retrospective analysis of one lab analyte over time. They describe it as de-identified because names are excluded. A flat refusal is not an acceptable answer. Deliverable: the column list you will actually provide with a justification per retained field, the sentence explaining why free text defeats an enumerated-identifier approach, your small-cell rule for the published stratification, and what you deliver this week.

Approach
  1. The probe is whether privacy is a design skill for you or a compliance reflex. Flat refusal and unquestioned fulfilment both fail, for opposite reasons.
  2. Reconstruct the analysis from the research question rather than from the request. A longitudinal trend in one analyte needs a stable pseudonymous subject key, the analyte's loinc_code, value_numeric, units, the reference bounds, and a date. It does not need names, notes, or a precise birth date.
  3. Replace each identifier with the least precise version that still answers the question: a salted per-study pseudonym instead of member_id, age in years or an age band instead of date of birth, a consistent per-subject date offset if only intervals matter, and a coarser geography than five-digit postal code.
  4. Explain the free-text problem in one sentence. Removing an enumerated list of identifier fields does not de-identify a note, because notes carry names, relationships, employers, dates and rare clinical detail in prose, so only a reviewed extraction into structured fields or a formal statistical determination addresses it.
  5. Set the publication rule before the analysis runs. Suppress cells below a stated threshold and suppress complements too, because a reader holding a row total and all but one cell recovers the suppressed count by subtraction.
  6. Keep them moving. Deliver the reduced extract into a controlled environment this week rather than onto a laptop, and offer to derive any note-based variable yourself as a structured flag so they never need the prose.
Follow-up
  • They say the age band loses resolution their model needs. What do you do?
  • How do you set the suppression threshold, and who signs off on it?
  • The analysis later needs linking to a second data source. What changes?
  • 01

    How do you handle missing or noisy data in a clinical research context?

  • 02

    Describe an analysis you delivered that was wrong, where someone acted on it before the error surfaced. Pick something with a mechanism you can name, not a typo. Cover what the number claimed, what was actually true, how much time passed before it was caught, who caught it, and what you told the people who had already acted. Deliverable: a five-minute account that ends with the specific control you added afterwards, plus one occasion since when that control has fired.

  • 03

    A researcher asks for a one-off extract covering 12,000 members: member_id, date of birth, five-digit residential postal code, full lab_result rows including value_text, and clinical note text, held on their laptop for a retrospective analysis of one lab analyte over time. They describe it as de-identified because names are excluded. A flat refusal is not an acceptable answer. Deliverable: the column list you will actually provide with a justification per retained field, the sentence explaining why free text defeats an enumerated-identifier approach, your small-cell rule for the published stratification, and what you deliver this week.

PracHub interview preparation framework ↗
Is this an official Seagen interview guide?

No. It is PracHub's own research and practice material for the Data Scientist role at Seagen. Rounds and questions reflect what candidates have reported, not a process Seagen has published, and they change over time. Confirm the current format and scope with your recruiter.

PracHub interview research ↗
How long should I expect the entire interview process to take?

The timeline varies, but from the initial recruiter screen to the final decision, it typically spans several weeks, reflecting the depth of the multi-round evaluation process.

PracHub interview research ↗
What is the most important thing to emphasize during the seminar presentation?

Focus on the "why" behind your technical decisions; emphasize how your data-driven approach directly supports the clinical or business goal at hand.

PracHub interview research ↗
How much weight is placed on domain knowledge in biology?

While you are hired for your data expertise, demonstrating an interest in or understanding of the drug development lifecycle will significantly differentiate you from other candidates.

PracHub interview research ↗
Sources & methodology 3 sources ↗

No official company page is cited. Rounds and questions come from candidate reports and PracHub editorial material; each source shows the date it was read.