Case Studies: The Low-Down

What is a case interview? To quote from the MIT Careers Handbook, it’s a situation where “you are introduced to a business dilemma facing a particular company. You are asked to analyze the situation, identify key business issues, and discuss how you would address the problems involved.”

Sounds challenging. But while case interviews are designed to push you, they shouldn’t make anyone faint in fear. Here’s a step-by-step guide that will have you tackling case study questions with confidence.


The basics

The main qualities that case studies assess are your ability to process information, evaluate risks, solve problems and deal with unusual situations. They can be on any topic and take pretty much any form – though many involve some form of maths. What they will always do is pose a complex, sometimes even unresolvable problem.

Apart from practising some previous examples, there are a few tips you can take on board. Always think aloud. This is not an exam but an interview; you are expected to voice your estimations and decisions. Work with the interviewer, not against her – if you’re lucky, they’ll help rather than hinder you in your discussion. In fact, you might be judged negatively if you shut the interviewer out; you want to prove you’re a team player, don’t you?

Prepare well. Check the company’s site beforehand, in case it has some sample questions available. Read through some famous cases from the past and try to understand how experts reacted to them. For estimation challenges, it helps to know some basic statistics (e.g. the world population in billions) but you can’t learn it all, and they won’t expect you to.

Finally, take your time. The interviewer would rather you took a careful, considered approach to a problem than rush to give a quick answer. With these questions, it’s all about the process.


How to answer a classic case study question

“A supermarket chain has noticed a decline in its profitability. They have hired you to find out why this is and to recommend and implement a solution.” (example from TargetJobs)

I hope you read that carefully, because being clear on the question is your first challenge in a case study. Listen to what is being said, take notes if necessary, and make sure you have a visual reference if a number slips out your head.

Ensure that you understand any technical terms. In this case, your prior research should have taught you what ‘profitability’ and ‘cost-effective’ mean – but in this case, it would also help to know ‘gross profit’, ‘net profit’ and ‘operating margin’. If you don’t know what something means, ask. Better to admit your lack of knowledge than reveal it through a bizarre calculation or response.

In the case above, the obvious first step is to work out why the profitability of this supermarket is declining. Suggest reasons to your interviewer, compiling a list, and possibly calculate which you think is the most likely.

The second action is to determine how to resolve each of these issues. If, for instance, the supermarket’s operating margin has risen, resulting in a decline in profits, you need to find a solution that will compensate for the additional costs.

Finally, determine any possible obstacles to implementing your strategies. If possible, find a way around them! If not, this step will at least show an awareness of common business problems and avoid your looking naïve.


… and a market sizing one

“How many people are wearing trainers on their London commute on any given morning?”

This kind of question is called ‘market sizing’. It challenges you to reach a general number based on well-informed ‘guesstimates’. Nobody expects you to get this right, as such – the process, and the way you tackle the question, is much more important than the answer. Basically, interviewers want to see how you tackle a difficult problem, and whether you can apply logic to an unfamiliar challenge.

Start by clarifying your terms. For example, does ‘wear trainers’ mean wear trainers all the way or just for part of the commute? Does the ‘London commute’ include students and children going to school, in all zones? You need to be very clear on the parameters within which you’re working.

Then, break down groups and numbers. You might know that the London population is about 8 million. Of these, you might estimate that 4 in 5 commute to school or work every day. So our commuter number would be 6.4 million.

If necessary, sub-categorise according to MECE principles – i.e. ensure that your sub-groups are all mutually exclusive, and collectively make up the whole. For example, let’s say you wanted to sub-categorise London commuters. Your groups may be:

  • Bus commuters
  • Overground commuters
  • Tube commuters
  • Boris bike commuters
  • Drivers
  • Walkers

However, there is overlap here; somebody could use both the overground and tube to reach work every morning. So these groups are neither mutually exclusive nor does their sum total equal the total of London commuters. You’d do better to go for:

  • Those who walk more than 2 miles in total on their commute
  • Those who walk 0.5 < 2 miles in total on their commute
  • Those who walk less than 0.5 miles in total on their commute

Then apply any calculations to these two groups separately, factoring in any unique issues. For example, people are less likely to wear trainers if they are walking less than 0.5 miles, but are very likely to if they are walking more than 2 miles. Apply these rules to the entire process, and you’ll come up with something close to the truth.

Case studies are not something to be frightened of. They are an opportunity to demonstrate the tenacity and independent thinking that makes you a great candidate. If you work things through as logically as possible, according to the above principles, then you will do well in the eyes of your interviewer. So get going – and good luck!


Susanna Quirke writes for Inspiring Interns, a graduate recruitment firm which specialises in sourcing candidates for internships and giving out graduate careers advice. To hire graduates or browse the graduate jobs London has to offer, visit our website.







Ksenija Kotova

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