How to Handle Case Interviews

General Overview

The route into this is to try to get into the mind of the interviewer and the requirements s/he is looking for.  For an analytic job it will probably include ……a quick logical and structured mind capable of handling complexity.  It will probably require a degree of numeracy and, in addition, an ability to listen and present complex information succinctly.

This is a formidable ask for most people, but there are three key things to remember….

  1. You must be confident and enthusiastic.  When presented with the Case Study try to appear the opposite of how you might feel – try to show that you are enthusiastic about the intellectual challenge use words like ….”that’s a really interesting question” or “I’m looking forward to working through this one”.
  2. Remember to actively listen.  In our experience the stress of the interview has frequently distorted the interviewee’s hearing and they start answering the wrong question or miss cues that their thought train is either irrelevant or boring. This is an easy one to practice – always ask questions or feedback your understanding.  For example …“So you would like me to work out the number of shoes presumably including Northern Ireland, Scotland and Wales” or “Is this a stand alone chocolate and confectionery factory or is it mult-site”
  3. The third thing to remember is to put structure into your thinking, if you just utter a stream of random ideas and thoughts it will lose the interviewer and certainly will not impress him/her.

Linked to 3 is a philosophical point which has some relevance.

The brain generally thinks in a linear way A=B and B=C, C=D, D=F …..therefore A=F.  But the brain receives information best in the reverse of this that is A=F because F=D, D=C, C=B and B=A. So in this example thinking aloud about the various steps might confuse the interviewer, but to say “I would like to take you through a logic train which shows A=F” would be much more powerful.

We have already mentioned that the Case Study is a consulting simulation.  In real life you would have a calculator and pencil and paper, so assume in handling the case that this is a given.  There may be exceptions that the interviewer will tell you about, he/she might for example say to you “ I would like to see how you handle these numbers in your head”.  Is there a calculator available? If not, suggest they use numbers rounded to nearest 100/1000? But stress importance of getting metal arithmetic right,

Do not be afraid of thinking!  Take time to ponder if you need it, but also use the techniques of gaining thinking time – asking questions is one way.  Summarising your understanding also will gain precious seconds when you can be thinking of the next step.

Much more so than in a conventional interview the Case Study is a dialogue, the interviewer will have information you need to ask him/her for and will usually give you encouragement and help if you are struggling.  Try to imagine the situation that you are colleagues working together but that you have to do all the work.

In any Case Study you may wish to, or be asked to, demonstrate your mental agility and numeracy. If you are in this position and you are dealing with large numbers do be careful to get the number of zeros right.  There is nothing worse than arriving at an answer which is out by a factor of 100 or 1000.  This is an excellent reason for building sanity checks into your structure.

The final point is about the stress of the interview.  In real life your views and conclusions are going to be challenged, sometimes aggressively.  A trained Case Study interviewer will want to find how far he can push a candidate intellectually and how well they can manage stress.  They will typically do this by layering the complexity of a case. The paradox here is that the more complicated the case is made during the course of an interview the more it is an indicator that the interviewer believes you are doing well.

The approach to Market Sizing Cases

We have already mentioned it will be a big mistake to suggest Googling the answer. The interviewer is expecting the interviewee to, in discussion with him/her, make a series of assumptions and estimates to arrive at a logical and reasonably accurate guess.  The interviewer is not looking for accuracy of answer but will be very interested in method and approach to the problem.  Structure, as in the Business Case, will be critical, it gives a road map and direction and helps the dialogue between the interviewer and the interviewee.

Lets examine one of the examples cases ….

How many petrol stations are there in the UK?

A good route into this case is to first think of a few ways of getting to your estimate and to discuss each of these with your interviewer.  So your opening, once you have fed back the question (thinking time and good practice to make sure you are answering the right question) might be “ that’s a really interesting challenge (showing some intellectual enthusiasm) there must be a few ways of getting into this such as ….

One way would be to estimate the number of petrol driven vehicles in the UK. Estimate the petrol consumption and then assuming supply = demand work out how many petrol stations would be needed to serve this demand.

This is complex and will involve a lot of estimates and guessing however it will probably lead to some sort of answer.

A better and simpler method might be to think about an area I know well and estimate and count the number of petrol stations in that area then figure out a way of extrapolating this nationwide.”

There are likely to be other ways you might think of.  Discuss the merits of each with the interviewer and with his/her help choose the one to follow.  The next step is to describe exactly what you are going to do.  In this example say you live in Chiswick and happen to know that there are 4 petrol stations within a square mile of where you live. You should say to the interviewer you are going to base a square mile estimate on information you have of a London suburb, then maybe test this against other areas to get a good estimate.  Then you plan to extend this to all the major urban city areas in the UK and finally make some estimates on rural areas.   This is your structure.

With some educated guesses and some relatively simple maths you will come up with an answer.  You then need to do some sensitivity analysis and credibility checks. A simple way would be to use another method to estimate.

In a memorable interview with a star Harvard Business School lady this was one of the Cases asked and very rapidly the candidate came to a sensible answer.  Modestly saying “but gee that’s only a crude guess maybe there’s another way I can do it……  We have just done a case study here at Harvard on the cremation industry and I happen to know how many crems. there are in the US.  I have had a really bad time in some ways with 9 of my close but elderly relatives dying recently and I have traveled to different states and cities to go to the funerals. In all cases I had a hire care and had to find a gas station to fill up before heading back to the airport so I am going to guess at the number of gas stations around crems then multiply by the number of crems!”

What a great answer. It showed flair and creativity, she got the job!

The Approach to Business Cases

One top tip for these kinds of Cases is to figure out, perhaps by asking directly, if this is a Case the interviewer has been or is working on at the moment. If so there is a propriety issue. Long hours have gone into the Case and the conclusion and the interviewer would like you to reach the same conclusions.  Also in this situation the interviewer will have a wealth of extra and helpful information. The dialogue with the interviewer will be key in these cases as will the non verbal clues if you are taking a wrong turn.  A good technique here is to try not to be too controversial or combative if challenged.

Generally speaking the more junior the interviewer the more likely it is that they will use something from their direct experience. It is also the case that the more junior the interviewer the less experienced they will be at Case Study interviewing; in some cases the only experience they will have had will be all the cases they faced during their selection.

Once you have established that you fully understand what you are supposed to be doing you must establish or reconfirm the core facts.  You may have been given these or be expected to have figured out that you have to ask for them. Lets say for the chocolate factory you are given

–          Total revenue and total cost

–          Market share and Market growth

–          Online vs Offline distribution channels

At this point it should be apparent what the main thrust of the case is, perhaps in this case tackling concerns about a company’s declining profitability.

Next step is to build a structure for attacking the problem. The first step is to identify the key parameters which might affect profitability.  Once these have been identified with the interviewers help choose one or two to examine in some detail.  In this example you might want to know

  • Who buys these products and are there particular market segments to address?
  • Are there substantial differential profits by product line and why?
  • What is the manufacturing cost per unit (maybe 1000) per product line?
  • How sensitive is the market to price changes and what is the competitor market pricing?
  • What are the best channels to market for these products and are there alternatives?

Your interviewer will steer you to the area that s/he is particularly interested in and then probably expect you to do some maths to come up with some conclusions.

Further Resources

There are many very good web sites with practice cases, some are listed below, but there is nothing to beat a live interview to gain confidence and experience.

Return to Case Study Intro here.