Assessment Methods
Work Sample Tests vs Interviews: Which Predicts Performance Better
5 February 2025
Every evidence-driven recruiter eventually faces the same fork in the road: work sample tests or interviews? One is the comfortable default; the other is quietly outperforming it on the only yardstick that matters—actual job performance.
Validity Face-Off: What the Data Says
Schmidt & Hunter’s landmark meta-analysis puts structured-interview validity at r = .51. Work sample tests edge ahead at r = .54.
That three-point gap equals roughly 16 % more accurate hires.
A 2021 HBR study of 259 UK fintech hires found top-quintile simulation performers generated 32 % more first-year revenue than high-scoring interviewees with identical qualifications.
Interviews rely on self-reported stories. Work samples observe behaviour in real time, shrinking the inference gap between test and job.
Where Interviews Still Win
Cultural Add & Motivation
Structured interviews shine when you need to gauge:
- Cultural add, not just “fit”
- Long-term motivation
- Growth potential in ambiguous roles
Cost & Familiarity
They’re cheap to schedule and socially familiar, so hiring-managers rarely push back.
Bias Warning
Yet similarity bias creeps in fast. A 2022 SHRM poll showed 57 % of UK managers preferred candidates who shared their alma mater or accent—even when CVs were identical. Drop the structured rubric and validity plummets to coin-flip levels (r = .2).
Work Sample Tests: Accuracy, Fairness & Candidate Trust
Work samples mirror the role: analysts model messy data, support agents triage a live chat queue, marketers launch a mini-campaign.
Fairness Boost
Standardised tasks give every candidate the same stimulus, slashing adverse-impact variance. IBM saw a 44 % rise in female and ethnic-minority hires after replacing panels with simulations.
Candidate Reaction
A 2023 Candidate Experience Foundation survey found:
- 78 % of applicants trusted the process when a work sample was included
- Only 54 % trusted interview-only processes
Transparency plus “try before you buy” cuts early-career attrition and saves an average £12,000 replacement cost per hire.
Layered Assessment: The High-Validity Combo
Top employers don’t pick sides—they stack both tools.
- Screening: 10-minute async work sample to shortlist
- Deep dive: semi-structured interview probing values alignment
- Final stage: day-in-the-life simulation with collaborative tasks and stakeholder Q&A
This hybrid lifts overall validity to roughly r = .63, capturing both can do and will do.
Cost, Logistics & ROI
Legacy simulations were pricey. Today’s AI platforms auto-generate job-specific tasks and score them instantly.
- Average spend: £20 per candidate
- Typical assessment centre: £400 per candidate
- Cost of a mis-hire (CIPD 2022): £30,000
Even testing 500 applicants, ROI hits 15×.
Quick-Start Playbook
- Start small: pick one high-volume role with clear KPIs
- Co-design tasks: ask top performers for “moments that matter”; convert the top three into 8-minute simulations
- Randomise data sets: prevents collusion while keeping scoring objective
- Use blind scoring: strip names and universities to reduce halo effects
- Track quality-of-hire: compare six-month performance ratings of interview-only vs work-sample cohorts; feed results back to refine weights
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