Casper vs. AAMC PREview vs. Duet: Full Comparison

Applicants sorting out which situational judgment test their schools expect often bounce between multiple pages and outdated spreadsheets.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 the delivery format, scoring language, and result timelines vary enough 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 sits on top of Casper as a program-fit survey that surfaces alignment between your values and each school's stated priorities.

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. 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 only available once you've booked Casper. It's an online values-alignment survey comparing your preferences to each participating program's stated priorities. The survey takes about 20 minutes, carries no additional cost, and must be completed within a set window of receiving the invitation. You never see a Duet score; programs review the match profile alongside your Casper quartile.

All three enforce one attempt per admissions cycle. Casper allows a retake only if Acuity verifies a technical failure on their end; PREview allows one administration per testing season; Duet can only be completed once per invitation. Plan your calendar around these limits, since none of them offer a routine do-over.

Which Schools Use Casper, PREview, or Duet

Requirements vary sharply by program and country:

• Casper is close to universal across Canadian MD programs and required by a growing share of US MD, DO, PA, and nursing programs, largely because it's the most established option internationally.
• 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 optional but encouraged at a number of programs, including some in the Acuity network, that put a premium on mission alignment and curricular fit alongside Casper.

A handful of schools 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 official 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 relies on honest self-reporting, not performance under pressure. Before completing it, jot a few notes on what you genuinely value in curriculum structure, mentorship style, and community engagement, since admissions committees compare your Duet profile against the themes in your secondary essays.

If a School Requires More Than One

If a program asks for Casper and PREview, or Casper paired with Duet, 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. Complete Duet within a few days of your Casper session, while each school's priorities are still fresh from your research.

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 test takers in your session. 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, PREview, and Duet test overlapping qualities through very different formats, and treating them as interchangeable is the fastest way to under-prepare for one of them. Confirm exactly which assessments your programs require, prioritize by registration deadlines, and use the official Casper practice scenarios to build the core reasoning skills that transfer across all three.

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