Attending interviews can be nerve-wracking enough without the added stress of being asked to do sums, but that’s exactly what you will be asked in a Case Study interview.
Banking firms and consultancies are increasingly using Case Study interviews to test candidates’ analytical skills and logical thinking capacity, and part of this process involves ‘guesstimates’. These can be both quantative and qualitive questions along the lines of ‘how many units are there in…?’, or ‘what is the market for….?’ Don’t let these leave you in a blind panic, the key to succeeding at Case Study interview is all about preparation. In his book The Complete Guide To Case Study Excellence, Arthur Krebbers, co-founder of ‘Generation 2 Generation’, states: ‘Guesstimates are an interviewer’s favourite tool. They separate the wheat from the chaff. They test you on all sorts of levels: reasoning skills, problem-solving skills, calculation, creativity. Not to mention your nerves. Fortunately, the guesstimate code can be cracked.’ Here are Arthur’s top tips.
1. Get yourself in a numbers mode
Get yourself thinking mathematically before the interview. Do some excercises to get those grey cells operating at full speed:
- Do all the multiplication tables again for the numbers one through to 12.
- Do some online numerical reasoning tests (there are a few free ones available on the web, such as http://www.assessmentday.co.uk/aptitudetests_numerical.htm)
- Open your school math books and try some of the excercises. If possible, re-learn the old paper techniques you learnt – especially for subtraction and division. If you want to go all the way, then fully surround yourself by numbers in the days before the interview.
2. Make the math easy
Round up or down as much as you can. If a sum looks hard, separate it into intermediate steps that are easier. Never let the numbers get the better of you. Also, when you find yourself taking more than five steps to get to an answer, alarm bells should go off. The numbers are all precooked, and getting the answers really shouldn’t take longer than a few minutes. ‘Don’t complicate matters
unnecessarily,’ Arthur advises. ‘They’re not looking for a whizzkid – they have computers and calculators to do the difficult math. If you need to know the UK population, assume 60 million. Trying to look clever by stating it’s 61 million
will make you look stupid when you have to divide 61 by something.’
3. Put it on paper
When you’re nervous, even the simplest sum will seem impossible. Putting all the figures on paper will help you calm down. Carefully write out all your steps – if need be number them.
4. Double check
Once you’ve done the sum on paper, go back to the start and check it again. Make sure you’re absolutely certain of the answer and the method before you give a definite number to the interviewer. Says Arthur: ‘If I had a penny for the number of times I messed up an interview due to a tiny mathematical oversight…’
5. Check for scale
Does your number make any sense? Say you’ve just calculated there are 400 million dish washers in the UK, and carelessly use that number in further calculations. What’s the interviewer going to think? It’s important you check for scale regularly, so as to ensure your numbers conform with reality. As one graduate recruiter puts it: ‘It does not matter if you got the calculation wrong, what matters is if you notice your error, and more importantly HOW you notice your error.’
Finally, as Arthur points out: ‘There are no good answers, only good methods. It’s not about the actual answer it’s about the path you take in getting there, so you need to focus on what seems to be the best route to take.’
The Complete Guide To Case Study Excellence is available to buy at www.casestudyexcellence.com for £7.50