AI for Consulting Interviews

AI for consulting interviews — case frameworks for MBB-tier prep

McKinsey, Bain, BCG — consulting case interviews demand structured problem-solving under pressure. Profitability cases, market entry, M&A, capacity expansion. PhantomCode runs you through case frameworks, mental math drills, and PEI behavioral, all with AI grading. See how the AI interview assistant works in a live interview.

Case framework drills (profitability, market entry, M&A)

The four canonical case types account for ~80% of MBB cases. PhantomCode drills you through profit-tree decomposition, market-entry checklists, M&A synergy frameworks, and capacity expansion analysis.

Mental math at consulting speed

Cases require fast arithmetic without a calculator. 14 × 87, 3.7M ÷ 0.42, percentage growth from base to target. The AI runs timed mental math drills calibrated to MBB superday speed.

Market sizing — top-down vs bottom-up

“How big is the global market for X?” Two approaches: top-down (start from population, segment) or bottom-up (start from a single unit, scale up). The AI helps you pick the right one fast.

PEI behavioral (McKinsey-specific)

Personal Experience Interview — McKinsey’s structured behavioral. Leadership, entrepreneurial-drive, personal-impact stories. STAR-format but with consulting-specific framing.

Hypothesis-driven problem solving

Strong consulting answers lead with a hypothesis. ‘I think the profit problem is on the revenue side because X. Let me test that.’ The AI grades whether your structure is hypothesis-led vs framework-recital.

Invisible to Zoom case interviews

Most virtual case rounds are recorded. The AI’s window stays out of the recording. You can run case-framework recall in real time without it appearing in the playback.

The four case types

The four canonical consulting case types

MBB cases come in roughly four flavors. Recognizing which one you’re in lets you load the right framework fast.

Profitability cases‘Profits are down 20%. Diagnose.’ Profit tree: Revenue (Price × Volume) and Cost (Fixed + Variable). Segment each branch.

Market entry / new product cases‘Should client X enter market Y?’ Checklist: market attractiveness, fit with client, mode of entry, financial outlook, risks.

M&A cases‘Should client acquire target?’ Synergies (revenue + cost), strategic fit, integration risk, deal value vs market value.

Capacity / operations cases‘Can client handle 2× volume?’ Bottleneck analysis, throughput math, expansion economics.

A profitability case in 7 minutes — example walkthrough

‘Our client’s profits dropped 15% YoY. Diagnose the issue.’

Clarify the question. “By ‘15% drop’, do we mean absolute dollars or margin? And is this industry-wide or client-specific?”
State your structure. “I’ll diagnose using a profit tree — break profits into revenue and cost, then drill into whichever branch is the bigger driver.”
State a hypothesis. “Given that the industry is healthy, I’d hypothesize this is client-specific — likely a cost issue, given how rare 15% revenue drops are.”
Ask for data. “Can I see revenue trend and cost categories over the period?”
Drill into the bigger driver. Say costs are up 20%. Drill into fixed vs variable. Say variable costs are up because input prices spiked.
Develop recommendations. Hedge inputs, pass through pricing, find substitutes, vertically integrate.
Summarize. “The 15% profit drop is driven primarily by a 20% increase in variable input costs. I recommend a three-track response: hedging, pricing, and substitution.”

Consulting interview behavioral — PEI and beyond

PEI (McKinsey-specific). Three universal dimensions: Personal Impact, Entrepreneurial Drive, Leadership. Have one story for each, 5-7 min each, with quantified impact.
Bain/BCG behavioral. Less structured than PEI. STAR-format works. Common prompts: leadership, conflict, ambiguity, growth, failure.
Why consulting? Specific, non-generic. “I love problem-solving” is a fail. Better: a specific moment that hooked you, a specific industry interest, or a specific skill you want to build.
Why our firm? Specific to the firm — practice areas, geographic strength, recent thought leadership, alumni you’ve spoken with.

When AI helps in consulting interviews

Yes: virtual case interviews. Sub-second framework recall. Hypothesis prompts. Math-check suggestions.
Yes: PEI prep. The AI grades story length, impact specificity, and dimension alignment (Personal Impact vs Entrepreneurial Drive vs Leadership).
Cautious: live mental math. The AI can verify your arithmetic, but interviewers expect you to do the math yourself. Use AI as a check, not a crutch.
No: in-person finals. MBB finals at the partner level are usually in-person.

Frequently asked questions

How long does consulting case interview prep take?

For MBB-tier targets: 6-12 weeks of focused prep is typical. The variable is case volume (need ~30-50 full mock cases) and PEI quality (1-2 weeks alone to nail the three stories). For tier-2 consulting firms: 4-6 weeks is often enough.

What's the most common consulting case type?

Profitability cases are the most common at MBB — they show up in ~40% of cases. Market entry is ~25%. M&A and capacity each ~15-20%. Drill profitability hardest; it's also the easiest framework to learn well.

Are AI tools allowed in consulting case interviews?

Candidate-side prep with AI is standard. For virtual case interviews, PhantomCode is invisible to Zoom recording. Use it for framework recall and math verification. The interactive nature of cases means AI assistance is harder to use covertly than in unidirectional Q&A interviews, but it still helps with sub-second framework loading.

What's the biggest case interview mistake?

Framework-recital without hypothesis. Strong candidates lead with a hypothesis and structure the case to test it. Weak candidates recite a framework (profit tree, 4Ps, Porter's 5 Forces) without committing to a direction. Interviewers can tell the difference within 90 seconds.

How important is mental math in case interviews?

Important enough that getting it wrong fails the case. MBB-tier candidates can do mental arithmetic at speed without a calculator. Drill specifically: 14 × 87, 3.7M ÷ 0.42, percentage growth, breakeven calculations. PhantomCode includes a mental-math drill mode.