Casper vs. AAMC PREview vs. Duet: Full Comparison
How Casper, AAMC PREview, and Duet differ in format, cost, and scoring, and how to prioritize prep if a school requires more than one.
Quick answer
Casper uses open-ended typed and video responses scored by human raters; AAMC PREview is a multiple-choice test scored against an official answer key; Duet is a free values-alignment survey that Acuity is now retiring. Most schools require only one, so check your program's admissions page before assuming you need more than one.
Applicants sorting out which situational judgment test their schools expect often bounce between multiple pages and outdated spreadsheets. This guide lays out where Casper, AAMC PREview, and Duet overlap, how they diverge, and what that means for your study schedule.
Each assessment measures non-cognitive competencies, yet Casper and PREview differ enough in delivery format, scoring language, and result timelines that they need distinct rehearsal blocks. Casper's video and written prompts demand confident delivery scored by human raters. PREview leans on policy-aware multiple-choice decisions scored against the AAMC's preprofessional competencies. Duet sat on top of Casper as a program-fit survey, but Acuity is retiring it, so for most applicants this is now a two-test decision.
Format, Timing, Cost, and Score Release
Casper is administered by Acuity Insights and runs 65 to 85 minutes across 11 scenarios split between typed and video responses, with each answer scored independently by a trained human rater. Registration windows open on a rolling basis, roughly every two to three weeks in peak season and about monthly outside it. Expect an $85 USD base fee for US Medicine, plus roughly $18-20 per additional school distribution, with results reaching schools 2-3 weeks after your test.
AAMC PREview is delivered directly by the Association of American Medical Colleges. It packs about 30 dilemmas into a roughly 90-minute multiple-choice test where you rank responses from most to least effective. Testing windows open in the spring and recur through the year, which makes it easier to schedule around secondaries. The fee is $100 USD, with fee assistance available for qualifying applicants, and scores typically arrive about three to four weeks after you test.
Duet is being retired by Acuity, which now shows an end-of-life notice for it. Where it still appears, it's an online values-alignment survey unlocked once you've booked Casper: about 20 minutes, no additional cost, completed within a set window of the invitation. You never see a Duet score; programs review the match profile alongside your Casper quartile. Treat it as optional unless a program tells you otherwise in writing.
Casper and PREview both enforce one attempt per admissions cycle. Casper allows a retake only if Acuity verifies a technical failure on their end, and PREview allows one administration per testing season. Plan your calendar around these limits, since neither offers a routine do-over.
Which Schools Use Casper, PREview, or Duet
Requirements vary sharply by program and country:
- Casper is required by 10 of Canada's 17 MD programs and by 26 US medical programs, with 2 more accepting it or PREview, plus a growing share of PA and nursing programs, largely because it's the most established option internationally. US osteopathic adoption is narrow: four DO programs require it for 2026-2027.
- AAMC PREview is used by a smaller, specific set of US MD programs that prefer a format mapped directly to the AAMC's own competency framework and comparable percentile-style bands.
- Duet is being phased out. Acuity now shows an end-of-life notice for it, and every osteopathic program that previously required or accepted it has dropped it for 2026-2027. Where it is still referenced, it's an optional values-alignment step rather than a scored requirement. Confirm directly with any program that still lists it.
Two US MD programs accept either Casper or PREview, and a few require both. Always confirm on your specific program's admissions page; see our medical schools requiring Casper guide as a starting point.
Prep Strategy by Test Type
Casper rewards fast, natural-sounding frameworks over polished scripts. Learn what raters look for in our scoring guide, then rehearse with the practice scenarios until you can cover the tension, stakeholders, action, and follow-up within the actual time limits. Rotate between typed and video prompts so both formats feel equally familiar.
AAMC PREview rewards precise prioritization rather than persuasive writing. Build timed drills that force you to rank the most and least effective response in each scenario, and review the AAMC's own sample items and rationale so you internalize how their scoring logic actually works. The ethical reasoning you build for Casper transfers directly.
Duet needs no rehearsal, and with Acuity retiring it, no prep budget either. If a program still asks for it, it relies on honest self-reporting rather than performance under pressure: jot a few notes on what you genuinely value in curriculum structure, mentorship style, and community engagement, then complete it and move on.
If a School Requires More Than One
If a program asks for both Casper and PREview, sequence your prep instead of splitting focus every day. Book Casper first, since its sessions are less frequent and score delivery takes longer. Once that's locked in, schedule PREview for a window that doesn't collide with secondary deadlines. If a program is still listing Duet, complete it within a few days of your Casper session, while each school's priorities are fresh from your research; it needs no study time.
Keep a simple log of which competencies each practice scenario exercised. If you notice a gap (for example, few resilience examples or thin policy reasoning), pull a targeted drill from the question-type guide rather than practicing the same strengths repeatedly.
Frequently Asked Questions
Is AAMC PREview easier than Casper?
PREview can feel more straightforward because you're ranking pre-written responses instead of composing your own, but the scoring is unforgiving: the AAMC compares your rankings to a specific answer key. Casper allows more nuance in how you express an answer, but raters still penalize vague or reactive reasoning. Prepare for both the same way: review ethical frameworks, then practice under real timing.
Do I need to take both Casper and PREview for the same school?
Only a small number of programs require both. Most either mandate one specific test or accept either. Check your program's admissions page directly, and if you do need both, reuse the same ethics and reflection prep across them rather than treating them as separate subjects.
How do Casper quartiles compare to PREview score bands?
Casper reports a quartile (1st through 4th) relative to everyone who took the same test type around your test date, not just the people in your sitting. PREview assigns you to a performance band based on the full testing population for that cycle. They aren't directly convertible, so track each result separately and note its release date and relevant deadlines for every program.
Which test should I prepare for first?
Whichever has the tighter registration window or earlier deadline for your programs. Casper sessions are typically less frequent than PREview's, so most applicants book and prepare for Casper first.
The Bottom Line
Casper and PREview test overlapping qualities through very different formats, and treating them as interchangeable is the fastest way to under-prepare for one of them. Duet, now being retired, needs confirmation rather than preparation. Confirm exactly which assessments your programs require, prioritize by registration deadlines, and use the Casper practice scenarios to build the core reasoning skills that transfer between the two that still matter.