Interviewer view · keep this screen to yourself

From a lab result to a replacement plan

You run the case. Read the prompt, answer questions from the notes below, and share data only when the candidate asks for it or gets stuck. Score at the end.

Case timer

00:00

Target length:

1. Read the prompt aloud

Read it slowly, then pause. Let the candidate ask questions before they structure.

Fictional and illustrative. Your PhD found that a delivery van battery loses 2 percent of its capacity every 100 full charges. A delivery firm in India charges each van once a day. It replaces a battery when it falls to 80 percent of its first capacity. Assume the loss is steady. When should the firm plan to replace its batteries?

2. Answers to clarifying questions

This case has no scripted clarifying answers. Answer from the prompt, and say "assume what you think is reasonable" if the prompt does not cover it.

3. A model structure

Compare the candidate's structure with this one. A different split can be just as good if it is clean and fits the problem.

Years until replacement = capacity the firm will give up / capacity lost per year
- Capacity lost per year: loss per 100 charges x charges per year / 100
- Capacity the firm will give up: 100 percent minus the 80 percent floor

4. The working, step by step

Each step shows how a strong candidate works it out. Share a new fact from it only when the candidate asks or is stuck, and let them do the math: the result in the dark box is what they should reach.

Step 1: Charges a year
What a strong candidate does: One full charge a day for a year.
Charges a year: 1 × 365 = 365
Step 2: Capacity lost a year
What a strong candidate does: 2 percent for every 100 charges, across 365 charges.
Capacity lost a year (percent): 2 × 365 ÷ 100 = 7.3
Step 3: Capacity the firm will give up
What a strong candidate does: From 100 percent down to the 80 percent floor.
Capacity the firm will give up (percent): 100 - 80 = 20
Step 4: Years until replacement
What a strong candidate does: Divide the capacity it will give up by the yearly loss.
Years until replacement: 20 ÷ 7.3 = 2.74

The recommendation to listen for

At the end, say: "The CEO walks in. What is your recommendation?"

Plan to replace each battery after about 2.7 years of daily charging. Budget for it from year 2. The main doubt is the steady loss: real batteries often fade faster near the end, so test a sample of vans each year.

Risks a strong answer names: Heat and fast charging can speed up the loss; The lab used full charges, but vans may charge partly.

Next steps: Log capacity on ten vans every quarter; Ask suppliers for the warranty floor and compare.

Score the candidate

Score each criterion from 1 to 5. A 2 or a 4 sits between the descriptions.

This case has no exhibit. Score Exhibit reading on how the candidate used the data you gave them: did they pick out the number that matters and say what it means?

Structuring

1: No clear structure, or a memorized framework that does not fit the problem.
3: A sensible structure, but with some overlap, a gap, or no clear priority.
5: A structure built for this problem, with no overlap and no gaps, a stated hypothesis, and a clear first step.

Math

1: Frequent errors, no units, or needed heavy help to finish.
3: Right answers but slow or messy working, or one error caught late.
5: Accurate and clearly narrated, with units, a sense check, and what the number means.

Exhibit reading

1: Read the chart aloud without finding the number that matters.
3: Found the key number but gave only part of the so-what.
5: Pulled the right number quickly and said what it means for the case.

Synthesis

1: Summarized what was done, with no clear answer.
3: Gave an answer, but with weak reasons or no next step.
5: Answer first, then two or three reasons with numbers, the main risk, and next steps.

Communication

1: Hard to follow: long silences, no signposting.
3: Clear most of the time, with some rambling.
5: Calm and concise, signposted each step, and checked in with the interviewer.

Total

0 out of 25

Score all five criteria to see the band and the feedback template.

Next: another case in Partner mode

Swap roles and run the next case, so you both practise answering and scoring.

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