Securing a Consulting Job – Cracking the Case Study Interview


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Don't hire someone without first tuning in for this essential advice.

So you've diligently applied to a range of suitable consultancies, your CV has won through the screening process- and ahead now lies the spectre of case study interviews! Never done one before? Well don't worry, the aim of this chapter is to give you a far better understanding of what you're likely to face and how to sail through the dreaded case study interviews.

By way of backdrop, let's talk first about traditional interviews and their limitations. Traditional interviews typically have your CV as the focal point for discussion -what have you done, why did you take certain decisions, what you would do differently, how did you feel when you accomplished certain things?

The problem with this type of interview is that a well-rehearsed candidate can usually come across in a very polished manner. With enough preparatory time, most blemishes can be professionally skirted over and explained away. The interviewer is left with the conundrum that they are seeing the side of the candidate that the candidate wants to portray, as opposed to what they want to see which is the real candidate and an accurate reflection of what they will be like to work with in a pressured environment.

Case studies leave a weak candidate exposed and draw attention to the shining stars. That's why consulting firms swear by them -and it's why you're likely to spend at least as much time during your consulting interviews working through case studies as you do talking through your CV and past experience.

So what are case study interviews and what is the interviewer looking to establish? Case study interviews come in a number of guises, but they are all effectively a role-play of life as a consultant. They are a chance for the interviewer to see first-hand how you perform under pressure, how you approach problems and how well you work with others.

In a nutshell, case study interviews will see you be given a 'real­life' consultancy problem to solve, requiring you to work with the interviewer just as you would in day-to-day life working on a project with members of the client team.

How many types of case study could I face?

Broadly speaking, there are two types of Case Study interview- and the good news is that both types can be prepared for and your performance will undoubtedly be enhanced with prior preparation of each type. You will see these two varieties of case study interview referred to in various ways, but our preferred terminology is:

• The market-sizing/mission impossible case study challenge.

• The condensed project assignment case study challenge.

The market-sizing/mission impossible case study challenge is the simpler of the two to describe. This type of question will take between 3 minutes and 15 minutes to answer, depending on the complexity/realism of the question posed. As such they are quite quick challenges, meaning a series of these questions will be thrown at you during a 45-minute case study interview, or you'll be peppered with them in spare moments during a regular CV interview.

The market-sizing/mission impossible challenge places you in the realms of a pressured day-to-day work environment. You need to deliver a certain output by a certain deadline - how would you go about delivering on that requirement? Or at its most base level, what would a back-of-the-envelope calculation look like to come up with a market estimate for a product/service that you know absolutely nothing about?

When faced with these questions, it's fair to say that you can expect none of your existing business knowledge to be of any value to you in answering the questions. In fact the whole aim of this exercise is to have the candidate move quickly from having no idea what the answer is to being in a position where they can propose a figure that sounds both plausible and logical.

Let's think of some examples:

• How many nappies are thrown into the rubbish in London each day?
• How many car tyres suffer a puncture in the UK each month?
• How many golf balls are lost on golf courses in the UK each year? 

Now imagine facing half a dozen questions like this in the space of a few hours of interviews and you can quickly see that no candidate is going to breeze through these challenges on the strength of the business knowledge they've brought into the interview room. It doesn't matter how varied and unusual a career you've had to date, you're not going to be at an advantage in knowing this kind of trivia.

The skill instead is to think about the challenges in terms of what you know - or could easily research - that would allow you to craft an answer as a back-of-the-envelope calculation that means the resulting answer sounds credible in terms of its magnitude. (Note: in all likelihood your interviewer will not know the exact answers either, so they'll just be looking for you to get to an answer that sounds plausible through the use of logic and creativity to address the fact that you don't know the actual answer.)

There's really no excuse for poor performance in this type of case study challenge. Pair up with a friend/family member/colleague and have them think of:

• Items to use in their questions (this could be just things they can see in the room they are in or out of the window they are sat by - so cars, computer screens, coffee mugs, carpets, etc.)
• The time period for each question - so 'each evening', 'each week', 'each month', etc.
• The action that needs to have happened - so 'manufactured in this time period', 'lost in this time period', 'become faulty in this time period', etc.

By stringing these together, your case study practice buddy should be able to fire off a series of these mission impossible challenges that you will answer as if you were sat there in the interview. No time to think about things, no choosing which questions you like and don't like- you have to answer every one of them as soon as you are asked them.

What you will find - in less than an hour of practising - is that you can transform yourself from someone who has no idea what the answer to these questions is and how you can tackle them, to someone who is instinctively thinking about what they do know and what assumptions they can make that will allow us to arrive at an answer that is the right order of magnitude.

By starting with an estimate of how many people there are in the UK and then applying conversion estimates (e.g. 5% of adults play golf; 20% buy a new car each year),you will quickly get to an answer that is the right order of magnitude through simple mental arithmetic in the interview room.

This is the simpler version of this type of case challenge, where the desired output has no real business significance and where you'll only spend a few minutes in reply to the question. The version that will last more like 15 minutes will see the interviewer pose you a question about e.g., a new product that's under consideration and where you're trying to estimate the potential revenue that that new product might generate. Your analysis will include a few more parameters and you'll probably be asked to describe how you'd tackle this problem if you had a couple of days in the office to produce your estimate. But fundamentally the challenge is just the same - come up with a market size estimate for a market that you knew nothing about when you walked into that interview room.

The condensed project assignment interview

There are many variations on this theme, but the essentials are the same. You will be put in the role of the project manager of a consulting project and be presented with just the information that was available to your team at the start of the project. So you'll in all likelihood be given a set of statistics, graphs and financial information so you have some idea of the situation facing your client. Your interviewer will probably play the role either of a Partner at the consulting firm (grilling you on progress of the project) or of a Director­ level member of the client team. Your task will be to:

• Correctly identify the problem faced by the client (i.e. the reason the consulting firm has been brought in is to...)
• Define the hypotheses that you would want to test during the course of such a project if you were going to be project managing this assignment for the next X months.
• As your interviewer shares with you further insights and data that were uncovered during the project, to draw conclusions regarding each of your hypotheses such that the consulting firm's final recommendation is made by the end of the interview.

A lot of what I teach our readers about tackling this type of case study question on our bi-monthly tutorial calls really needs us to be walking through a live example and critiquing how candidates then respond to the pressured interview situation. However, there are certainly some pointers you can take away from this guide in terms of how you should respond in your interviews:

1. Remember that your approach to solving the problem is far more important than any business knowledge you have about the particular sector or challenge being faced. The interviewer wants to know how well you can cope with being put onto an assignment in a sector about which you have no prior knowledge- as this is very often the situation with which you're faced in real life. So make sure you are solving the case through your interactions with the interviewer and your analysis of the information they present you, rather than relying on prior knowledge you may have about the particular sector that the case challenge is based around.

2. Your approach to the case study should be i) logical/structured; ii) comprehensive; and iii) collaborative.

3. You must act and not react to the situation. Do not blurt out ideas as they come into your head. Buy yourself some time to think through the problem and to structure how you would go about solving it.

4. Your absolute first response in a case study should be to ASK QUESTIONS!
- Asking questions will give you precious moments to think about the problem and how you might structure your response;
- It will probably also provide you with further information that may help to steer your answer in the right direction;
- It will allow the interviewer to steer you back on the right course if they can see you are thinking about the problem in totally the wrong way (which often surprises readers, but it's far easier to assess candidates who've tackled a case like-for­ like than to try and make an apples and pears comparison of candidates who tackled it completely differently).

5. Try to build up a graphical representation of the problem that looks like a tree/decision diagram. This structures your answer and helps you to see if your approach is comprehensively covering all angles.

6. Try to avoid making statements and instead ask collaborative questions (e.g., would I be right in concluding that... it would appear that... am I on the right track?).

Practise these types of cases with a partner - you'll find plenty of examples on consulting firms' websites - and you will find you become noticeably more confident about how to tackle them and how to interact with the interviewer after just a handful of practice runs.

This piece is reproduced from The Definitive Guide to UK Consulting Firms, a 400+ page careers guide for candidates looking to pursue a career in management consultancy. A free resource published by, this guide contains over 100 pages of career editorials followed by a directory of consulting firms active in the UK market - with over 380 employers listed and 189 employers profiled. The guide is free to download in PDF format, with hardback copies also available from October 2011 onwards. Access your copy of The Definitive Guide to UK Consulting Firms (2nd Edition).

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