Questions regarding McKinsey case interviews

Case Interview Framework McKinsey
Recent activity on Sep 27, 2018
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James asked on Sep 26, 2018

Hello guys,

I have been preparing a lot for my McKinsey interviews, and so far it's been extremely helpful. I passed the PST exam and now hoping to replicate the success with the rest of the interview process with your help.

There are some questions I'd like to consult with you on and would greatly appreciate your feedback:

1. I seem to never have enough time to write out my entire framework under 1 minute, even when all I do is penciling down the frameworks from mock case interviews onto paper. I suspect in real live situation, under stress, it would take me at least 10 seconds to think about the whole structure of framework tree, 15 seconds to write out the 3 big areas, leaving me with only 35 seconds to write out the branches for each area. This is only if I write very fast. When trying to write more legibly, I can take up to 2 minutes. So I must be doing something wrong.

Would it be okay to only write a keyword or two when constructing the branches (like "tech"), or in whole phrases (like "acquire key tech")? I was under the impression that my papers would be collected after the meeting for further evaluation by the interviewer, and so things should be clearly defined on paper?

2. While talking through my framework, if I suddenly notice an item I'd missed, would it be appropriate for me to add onto the framework as I speak?

3. At the end of quantitative questions, when I form mini-conclusions and tie them back to the initial question, would it be okay to pause and write these mini-conclusions on paper (so I can come back to it during the "Recommendation" phase), or would it appear disruptive?

4. I heard you can bring your own papers (most people recommend graph papers) into the interview. Would it be okay to pre-label them, so I can appear organize and save time from writing the labels? Like "Business Situation", "Objective", "Clarifications", "Calculations"...etc.

5. During the "Recommendation" phase, I would need to draw findings from all my previous analysis, including key observations, potential risks, areas worth exploring further...etc. It appears that it would be a good idea to label these things as I encounter them through the case, instead of trying to identify them at that last moment. Would you recommend that I color-label them (risk area is red, evidence supporting my hypothesis in green), or that I dedicate a separate sheet of paper to write down these key findings? If it's the latter, I am not sure whether I'm allowed to have time to do that?

Thank you for your patience and I'd greatly appreciate any suggestions on these questions!

Best Regards,


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Anonymous replied on Sep 27, 2018

Hey James!

First, congratulations on passing the PST! You have written a quite long list of questions, and I’ll do my best to answer below.

  1. To answer your question, it is absolutely fine to write short form, use acronyms (e.g. π instead of profit, R instead of revenue). Your papers are purely for your use and will not be evaluated at the end. If your interviewer asks to collect them, this is likely just for confidentiality reasons (i.e. they don’t want you to go sharing content from their case with other applicants).
  2. This is a very good question. The answer depends on a couple factors:
    1. If you realise there is an additional item you would want to look at under a branch as you are going through that branch, it is 100% fine to mention additional things at the end and jot them down – your structure does not necessarily have to be 100% exhaustive within the 1-1.5 minutes you had to make it!
    2. If you come up with an additional big branch you want to cover, it is fine to add it at the end - e.g. you forgot to include competition but remember mid way through, saying “finally, I would also want to look at competition…” and drawing this out as you speak.
    3. If you notice after covering a branch that you forgot a sub-detail of the branch (e.g. looking at growth rates), it also depends. If it’s a minor point, like “oh, I could have also looked at the industry life cycle” I would probably not go back – but maybe try keep it in mind while you go through that branch, and asking it if it’s still relevant. However, if you realise you missed something big, it might be worth pausing and saying “I’m sorry, I forgot to also say we should look at X under the industry” and quickly adding it on.
  3. Yes and No – it is ok for you to jot down and note, but I wouldn’t spend the time to fully write out the conclusion. For example, if you figure out one market segment is growing much faster than the others, instead of writing out the full form, just putting a box around the number and highlighting with a brief note like “HIGH GROWTH” would be enough. As long as you can understand it, it’s fine!
  4. Yes, you can bring your own paper, and graph paper is useful both for calculations and for making a neater issue tree. However, I would not pre-write on it – firstly, you never know what case you will get (e.g. it could just be a brain teaser – in which case your structure won’t make sense. Secondly, you can’t predict how much space you will need for a question. Thirdly, it just doesn’t have that much value and I don’t think it would really impress an interviewer enough to be worth the hassle/risk mentioned.
  5. A useful tool is, as going through the case, highlighting key insights you uncover – e.g. with a thick box, or what I used to do – a big star next to key pieces of information insights. You can also put a small box at the top of your sheet with “insights” and as you uncover details, put them here. This is similar to what you mention of “having a separate sheet for key findings”. Note that this doesn’t have to take long at all because, as previously mentioned, you can use short forms just to remind yourself “e.g. SEG. A – HIGH GROWTH”. However, I would not go as far as colour labelling. I think this is taking it too far and ultimately won’t be that useful. In the end, you would spend more of your time / brain power on colour coding instead of solving the case.

Hope this is helpful!


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James on Sep 27, 2018

Hello Alessandro, thank you so much for your detailed and extremely helpful replies! Assuming my papers would be collected after the interview, I had developed some very bad habits that greatly hampered my efficiency in answering questions. So now I must learn to un-learn those habits. Fortunately, your feedback was informative enough and I still have a week to prepare before the next round. I will prepare accordingly and hopefully can pass it. Many thanks again sir! Can't express enough how much I appreciate your help! If I get the offer in the end (should be end of October), I'll come here and personally thank you again!

Anonymous A updated the answer on Sep 26, 2018

I'm not sure about most of your questions because I've not interviewed yet, but from the perspective of a former teacher who needed to switch colors/pens frequently, I would definitely not recommend trying to use multiple colors.
Of course bring extra pens in case yours happens to run out of ink/you lose one, but the most disruptive thing out of all of the things you mentioned (in my opinion) would be switching pens often. It takes time, it's a clunky, it's not necessary, and honestly 10 mintues into the case you are highly likely to use the wrong pen for something and completely trip yourself up. This happened to me sometimes grading papers and that's a very low stress situation! Save yourself that pain and stick with one color!

If you want to label things, stick to something simple and easy for both you and the interviewer to remember (write a big R beside it for Risk and H for Hypothesis or something similar).

Best of luck with your interviews, congrats on where you're at!!


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James on Sep 27, 2018

Hi thank you for your reply, especially on the advice on not color-label my analyses. I will use abbreviations, "R", "H" as you had suggested. Thank you!