How do you choose the appropriate statistical model for a dataset?

Start by describing the question you want to answer, the outcome type, and the structure of the data. Explain how those elements guide model selection, for example choosing linear regression for continuous outcomes, logistic regression for binary outcomes, and mixed models when data are clustered or longitudinal. Give a short example such as analyzing repeated measures from a clinical trial, where you would consider a linear mixed effects model to account for within-subject correlation and fixed effects for treatment and time. Mention checking assumptions with residual plots, assessing model fit with information criteria, and comparing alternatives when necessary. Finish with practical tips, like preferring simpler models when they meet assumptions, documenting why you picked a model, and avoiding overfitting by penalizing complexity or using cross-validation. Avoid saying a particular software automatically dictates the model; focus on the data and scientific question first.

How do you handle missing data in your analyses?

Describe your stepwise approach: quantify the amount and pattern of missingness, consider whether data are missing at random, and choose an appropriate strategy such as multiple imputation, likelihood-based methods, or sensitivity analyses. Emphasize how the missingness mechanism affects your choice and interpretation. Give a concrete example, for instance using multiple imputation with chained equations for baseline covariates in a trial, then pooling results across imputed datasets following Rubin's rules. Explain that you would compare complete-case results to imputed results and run sensitivity analyses to check robustness. Offer practical cautions, like avoiding single imputation methods that understate uncertainty, documenting your assumptions about missingness, and communicating limitations to clinical colleagues so they understand how missing data might affect conclusions.

Explain how you would design a randomized clinical trial to test a new treatment.

Start by outlining the primary objective, specifying the primary endpoint, defining inclusion and exclusion criteria, and choosing an appropriate allocation ratio and randomization scheme. Discuss sample size calculation driven by the expected treatment effect, acceptable type I error, desired power, and assumptions about variance or event rates. Provide an example such as designing a two-arm superiority trial with a continuous primary endpoint where you estimate variance from pilot data, inflate the sample for potential dropout, and include stratified randomization by site to balance important covariates. Mention interim analyses and data monitoring plans when safety or efficacy stopping is plausible. Conclude with practical tips like documenting the statistical analysis plan before unblinding, planning how to handle multiplicity if there are multiple endpoints, and collaborating early with clinicians and data managers to ensure feasibility and data quality.

What is survival analysis and when would you use a Cox proportional hazards model?

Explain that survival analysis deals with time-to-event data and accounts for censoring when participants leave a study or have not experienced the event by last follow-up. The Cox proportional hazards model estimates the relative hazard between groups while adjusting for covariates without specifying a baseline hazard function. Offer an example such as comparing time to disease progression between treatment arms in an oncology trial, where you would check proportional hazards assumptions with Schoenfeld residuals and consider time-varying coefficients if the assumption fails. You might use Kaplan-Meier plots for unadjusted comparisons and the Cox model for adjusted analyses. Provide practical cautions, like verifying proportional hazards rather than assuming it, reporting hazard ratios with confidence intervals, and considering alternative models such as accelerated failure time models when hazards are not proportional.

How do you control for multiple comparisons in a study with many endpoints?

Describe the rationale for controlling the family-wise error rate or the false discovery rate, and explain common methods such as Bonferroni correction for strict control and Benjamini-Hochberg for weaker control focused on discovery. Emphasize prespecifying primary and secondary endpoints to reduce the need for heavy correction. Give an example where you have several secondary endpoints in a trial: you might primary-test the main endpoint at the usual alpha and adjust secondary endpoints with hierarchical testing or stepwise gatekeeping to preserve interpretability. For exploratory biomarker analyses, you might report adjusted p-values using false discovery rate control and clearly label results as exploratory. Finish with practical guidance: clearly state which corrections you applied in the statistical analysis plan, avoid mass testing without rationale, and discuss trade-offs with clinicians so the team understands how adjustments affect power and interpretation.

Describe your workflow to ensure reproducible and validated statistical analyses.

Explain a reproducible workflow that includes version control for code, using script-based analyses in R or Python, literate programming for combining code and reports, and containerization or environment management to freeze package versions. Highlight automated checks, unit tests for functions, and peer code review as part of validation. Provide a specific example such as writing analysis scripts in R with targets or Makefiles to run steps in order, storing data dictionaries, and using git branches for analysis, followed by a code review where a colleague runs the scripts against a snapshot of the data. Mention producing reproducible reports and archiving the final code and seed values so results can be regenerated. Add tips like writing modular functions for repeated tasks, validating intermediate outputs against known summaries, and including clear comments and README files so someone else can follow the analysis without guessing assumptions.

How do you communicate complex statistical results to non-statistical stakeholders?

Start by describing the audience, their goals, and the decision they must make so you can tailor the level of detail accordingly. Use plain language, focus on the practical implications of results, and present uncertainty with familiar terms like ranges or probabilities rather than technical jargon. Give an example such as explaining an adjusted treatment effect to clinicians by saying the treatment reduced progression risk by X percent with a confidence interval, then translating that into absolute event differences and expected outcomes per 100 patients. Use visual aids like simple plots or risk tables, and be ready to walk through assumptions if asked. Finish with communication tips such as preparing a one-slide summary for executives, having backup slides with methodological details for technical audiences, and inviting questions so you can clarify misunderstandings before decisions are made.

Which statistical software and packages do you commonly use, and why?

Explain that you choose software based on the task, regulatory requirements, and team workflows, and mention familiarity with R for flexible analyses and visualization, SAS for regulatory submissions and clinical trials, and Python for data wrangling and machine learning pipelines. Clarify that knowing multiple tools helps you pick the most appropriate one for reproducibility and audit trails. Give a concrete example such as using R and the survival and lme4 packages for exploratory modeling, SAS for final tables submitted to regulators, and Git for version control of scripts. Note that you follow the organization's standards when preparing outputs for submission, and adapt code style to match team conventions. Offer practical advice: highlight code you have reproducibly documented, be ready to explain why a particular package was chosen, and avoid implying that one tool is universally superior without context.

How do you handle data quality issues discovered late in an analysis?

Describe a structured approach: assess the scope and source of the issue, quantify how it affects key variables, and determine whether corrections, exclusions, or sensitivity analyses are appropriate. Communicate the problem and proposed remedies to the project lead and stakeholders before changing analysis plans. Provide an example such as discovering inconsistent date formats that shift baseline timing, where you would trace the issue back to the data extraction step, correct parsing rules, and rerun key summaries to see how results change. Conduct sensitivity analyses and document any changes to datasets and code so reviewers understand the impact. Conclude with practical cautions like avoiding ad hoc fixes without documentation, flagging any changes in the analysis plan, and planning additional validation steps to reduce the chance of repeat issues in future projects.

Explain a statistical method you frequently use for longitudinal data analysis.

Start by naming a commonly used approach, such as linear mixed effects models, and explain why they are useful for longitudinal data because they account for within-subject correlation and can handle unbalanced measurement times. Describe fixed effects for population-level estimates and random effects for individual deviations. Offer an example analyzing repeated biomarker measurements over time where you include random intercepts and slopes to model individual trajectories, test time by treatment interactions to assess differential effects, and check residuals and random effects distributions for model fit. Mention alternatives like generalized estimating equations when you want population-averaged estimates. Finish with tips such as centering time variables to improve interpretability, being cautious about overfitting random effects with small sample sizes, and reporting both model diagnostics and sensitivity checks in publications.

Tell me about a time you had to persuade clinicians to change an analysis plan.

Situation: In one trial, clinicians expected a particular subgroup analysis that risked multiple-testing problems and unclear interpretation. Task: You needed to propose a plan that balanced clinical interest with statistical validity so the study conclusions would be credible. Action: You prepared a concise memo showing potential false-positive rates under different approaches, proposed a pre-specified hierarchical testing strategy, and met with clinicians to explain trade-offs using simple visuals and examples. You incorporated their key clinical questions into a limited set of pre-specified analyses and suggested exploratory analyses clearly labeled as such. Result: The team agreed to the revised plan, which reduced the risk of misleading findings and maintained clinician confidence. The trial report was accepted with no major statistical concerns and clinicians felt their priorities were acknowledged.

Describe a time you missed a deadline and how you handled it.

Situation: During a busy reporting period you underestimated time needed to clean a new data source, which threatened the delivery of a safety report. Task: Your responsibility was to produce a defensible report quickly while managing expectations. Action: You communicated the delay immediately to stakeholders, prioritized the most critical analyses for the initial deliverable, and delegated data checks to a trusted colleague while you completed the core summaries. You documented the issue and proposed a revised timeline with contingency steps to prevent recurrence. Result: Stakeholders received an initial report on schedule covering safety-critical endpoints, with a follow-up complete dataset analysis delivered one week later. Your transparency preserved trust and the team adopted new checkpoints to catch similar problems earlier.

Give an example of resolving a conflict within a multidisciplinary project team.

Situation: On a study team, data managers and clinicians disagreed about acceptable outlier handling which affected primary endpoint summaries. Task: You needed to reach a reproducible, defensible approach acceptable to both groups. Action: You facilitated a meeting to align on the scientific rationale, showed how different outlier rules affected results with side-by-side analyses, and proposed a compromise of predefining objective outlier rules plus sensitivity analyses. You ensured the final decision and rationale were written into the analysis plan. Result: The team adopted the agreed procedure, reducing future disputes and improving the audit trail. The transparent process increased confidence in the final results and streamlined subsequent data queries.

biostatistician Interview Questions: Complete Guide

You can expect biostatistician interview questions that test both your statistical thinking and your ability to communicate results to clinical teams. Interviews often combine a technical take-home or whiteboard task, a discussion of past projects, and behavioral questions, so prepare for a mix of formats and question types.

Common Interview Questions

Behavioral Questions (STAR Method)

STAR Method: Structure your answers using Situation, Task, Action, and Result to tell compelling stories about your experience.

Questions to Ask the Interviewer

Show your interest by asking thoughtful questions

•How does the team prioritize statistical questions when clinical timelines and data readiness conflict?
•What are the common data sources and data quality challenges this team faces on new projects?
•How is the statistical analysis plan reviewed and approved within your organization prior to unblinding?
•Can you describe the team structure, including who you collaborate with for data management and regulatory affairs?
•What opportunities are there for methodological development or publishing within this role?

Interview Preparation Tips

Before the interview, prepare two concise project stories that highlight methods, your role, and measurable impact, and practice explaining them in plain language.

Bring a short portfolio or slide with reproducible workflow examples, such as a script and a figure, to illustrate your approach to analysis and validation.

When answering technical questions, state your assumptions explicitly, describe diagnostics you would run, and note alternatives if assumptions fail.

Ask clarifying questions when a problem statement is vague, and restate the question before answering to show structured thinking and reduce misinterpretation.

Overview

A biostatistician interview evaluates both technical skill and domain judgment. Expect questions on statistical theory (e.

g. , hypothesis testing, confidence intervals), applied methods (survival analysis, mixed models, multiple imputation), and programming in R, SAS, or Python.

Typically, employers include one or more of these: a 30–90 minute technical screen, a 60–120 minute on-site case study or whiteboard session, and sometimes a 24–72 hour take-home coding assignment. In practice, 60–80% of roles test coding ability; 50–70% probe clinical trials or public-health study design; and 30–50% include a data-cleaning exercise.

Interviewers look for three concrete abilities: (1) calculate and justify sample sizes (for instance, design a two-arm randomized trial to detect a 15% absolute difference with 80% power), (2) implement and interpret models (Cox PH hazard ratios, mixed-effect ICCs), and (3) communicate results to nonstatistical stakeholders (produce one clear figure and a 2–3 sentence takeaway). In addition, regulatory knowledge matters for pharma jobs: expect questions on ICH E9, multiplicity, and interim monitoring approaches such as O’Brien–Fleming.

Practice with real data, rehearse concise explanations (30–60 seconds) of key methods, and prepare one to three portfolio examples (GitHub, reproducible RMarkdown or Jupyter notebooks). Actionable takeaway: plan 20–40 hours of targeted prep covering coding, study design, and two short portfolio pieces.

Key Subtopics to Prepare

Focus your preparation around specific subtopics that interviewers frequently test. Below are high-impact areas with concrete examples and practice tasks.

•Study design and sample size
•Concepts: power, alpha, type I/II errors, noninferiority margins.
•Practice: compute sample sizes for binary outcomes (e.g., detect 10–20% absolute difference at 80% power); justify assumptions (baseline rate, attrition 10–20%).

•Survival analysis
•Concepts: Kaplan–Meier curves, Cox PH, proportional hazards assumption.
•Practice: interpret hazard ratio 0.7 (30% risk reduction); check PH using Schoenfeld residuals.

•Longitudinal and mixed models
•Concepts: random intercepts/slopes, intraclass correlation (ICC).
•Practice: explain why ICC of 0.05 vs 0.2 changes sample size; write lmer syntax and interpret fixed effects.

•Missing data and causal inference
•Concepts: MCAR/MAR/MNAR, multiple imputation, propensity scores.
•Practice: choose imputation method for 15% missingness and justify sensitivity analyses.

•Programming and data wrangling
•Tools: R (tidyverse, data.table), Python (pandas, statsmodels), SAS macros.
•Practice: write a reproducible script that cleans, summarizes, and models a 10,000-row dataset.

•Regulatory/statistical principles
•Concepts: multiplicity, interim monitoring, estimands (ICH E9).
•Practice: propose a multiplicity control plan for 3 primary endpoints.

Actionable takeaway: build one 2–4 hour project for each subtopic and rehearse a plain-language summary (≤3 sentences).

Practical Resources and Study Plan

Use a mix of books, courses, datasets, and coding practice. Below are vetted resources with estimated time commitments and specific uses.

•Books (read 1–2 chapters per week)
•"Applied Linear Statistical Models" — focus on 3 chapters on linear mixed models (≈150 pages to scan).
•"Survival Analysis Using S" or Hosmer & Lemeshow — read 100–200 pages on Cox models.

•Online courses and tutorials (2–6 weeks each)
•Coursera: "Design and Interpretation of Clinical Trials" (4 weeks) — emphasizes sample size and endpoints.
•DataCamp / Datacamp-like modules: 20–40 short R/Python exercises on regression, survival, and tidy data.

•Practice datasets and repos
•Kaggle: use COVID-19 hospital datasets or clinical-trials datasets to practice survival and mixed models (10,000–100,000 rows).
•GitHub: follow 2–3 biostatistics project repos; replicate one analysis and document it.

•Coding practice and challenges
•Do 30–50 coding problems: data cleaning, joins, reshaping, and model fitting. Timebox to 60–90 minutes per exercise.

•Regulatory & guidance
•Read ICH E9 summary (10–20 pages) and an FDA guidance on multiplicity or interim analysis.

Actionable takeaway: commit to a 6–8 week plan: 40–60 hours total, split into coding (40%), theory (30%), and portfolio work (30%).

biostatistician Interview Questions: Complete Guide

Michael Rodriguez

Common Interview Questions

Behavioral Questions (STAR Method)

Questions to Ask the Interviewer

Interview Preparation Tips

Overview

Key Subtopics to Prepare

Practical Resources and Study Plan

Interview Prep Checklist

Build your job search toolkit

biostatistician Interview Questions: Complete Guide

Michael Rodriguez

Common Interview Questions

Q1How do you choose the appropriate statistical model for a dataset?

Q2How do you handle missing data in your analyses?

Q3Explain how you would design a randomized clinical trial to test a new treatment.

Q4What is survival analysis and when would you use a Cox proportional hazards model?

Q5How do you control for multiple comparisons in a study with many endpoints?

Q6Describe your workflow to ensure reproducible and validated statistical analyses.

Q7How do you communicate complex statistical results to non-statistical stakeholders?

Q8Which statistical software and packages do you commonly use, and why?

Q9How do you handle data quality issues discovered late in an analysis?

Q10Explain a statistical method you frequently use for longitudinal data analysis.

Behavioral Questions (STAR Method)

B1Tell me about a time you had to persuade clinicians to change an analysis plan.

B2Describe a time you missed a deadline and how you handled it.

B3Give an example of resolving a conflict within a multidisciplinary project team.

Questions to Ask the Interviewer

Interview Preparation Tips

Overview

Key Subtopics to Prepare

Practical Resources and Study Plan

Interview Prep Checklist

Build your job search toolkit