Practice cases with a partner

Agree what you are practising

A case session is more useful when both people know its purpose. Decide whether this is a full interview simulation, a supported learning session or a focused exercise such as an opening or exhibit discussion. In a simulation, frequent coaching changes what you are measuring. In a learning session, withholding every hint may prevent the candidate from practising the step they came to improve.

Agree the case format, approximate time and how hints will work. The interviewer should read the material beforehand and understand the exhibits and calculations. Use material you are entitled to use, and avoid presenting a remembered question from a confidential real interview as a practice asset. CaseMentor's practice cases are original fictional exercises.

Choose one specific learning goal. You could practise distinguishing revenue drivers from cost drivers, explaining why a dataset is needed, or giving a recommendation with a decision threshold. You can observe other things too, but a single focus makes it easier to recognise whether the session helped.

Write down events rather than impressions

Feedback such as "be more structured" is difficult to act on. Record the moment that prompted the feedback. For example, the candidate grouped customer acquisition and total marketing cost in separate branches, then counted acquisition spending in both. A specific observation lets you explain the impact and practise an alternative.

Distinguish an error from a different defensible approach. A candidate may choose another decomposition and still reconcile the figures correctly. Ask them to explain their logic before insisting on the written solution's route. Assess whether the candidate's reasoning supports the answer.

Use hints deliberately

If a candidate is stuck, offer a prompt that helps them continue the work. You could ask, "What decision will this calculation inform?" or "Which units should the answer have?" If more help is needed, make the hint more specific. Record when you intervened so the candidate knows which step to retest independently.

Do not let a calculation error silently contaminate the rest of a learning session. Ask for a reasonableness check or correct the number once the source of the error is understood. The remaining case may still offer valuable practice in interpreting evidence and making a decision. In the debrief, separate the original error from the later reasoning that used the corrected figure.

Let the candidate reflect before giving your view

Ask the candidate what they think worked, where they lost the thread and which part they would redo. Then compare that account with your observations. A candidate may worry about a long pause while overlooking that they never established the client's target. Compare those concerns before deciding what to practise.

Choose one or two strengths to repeat and one or two changes with the largest effect. For each change, state the moment, its consequence and a better action. "When you used total revenue as the benefit of the extra customers, the investment appeared attractive even though their variable costs exceeded the revenue. Next time, calculate incremental contribution before comparing it with the investment."

Keep your judgement calibrated. Base your feedback on the attempt you observed. Avoid translating a small sample into a claim that someone will definitely pass or fail. You can be direct about an error without pretending to know a firm's private scoring or a candidate's final outcome.

Turn feedback into a retest

End with a next action that includes the task and the evidence of improvement. "Redo the same case" may mostly test memory. A better follow-up is three fresh contribution questions, followed by a new case in which the candidate must decide which costs are incremental. Revisit the skill after a gap and note whether a hint was needed.

For solo work, use the same method. Write your answer before revealing the worked response, compare the reasoning and record the specific divergence. Use the case log for a concise takeaway and a dated next action. Over time, look for repeated error types rather than simply counting completed cases.