Daily work - good at math calculation, but lack "sensitivity to numbers". How to improve?

Quantitative skills
New answer on Jun 09, 2020
10 Answers
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Anonymous A asked on Jun 07, 2020

My quantitative skill is above average, and I could do calculations fast (which is a common feedback I get during case interview practices). However, in my daily job, my manager gave me a feedback that my "sensitivity to number" is not good since I had made careless mistakes in typing numbers a few times. I know a way to improve is to always "double check" the figures, but I'd like to know how to improve my sensitivity to number? Some of my friends who are "sensitive to numbers" mentioned that they could remember numbers very naturally and easily, but it seems that I need to spend extra effort to do this. How could I be more "sensible to numbers"?

Appreciate any advice! Thanks.

(edited)

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Robert
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replied on Jun 07, 2020
McKinsey offers w/o final round interviews - 100% risk-free - 10+ years MBB coaching experience - Multiple book author

Hi Anonymous,

Mistakes/carelessness in numbers is an absolute show-stopper in reality (and it also becomes a red flag in interview situations as well).

Let me explain why. Whenever I am the partner on a project, I need to be 100% sure and confident that the numbers are correct. I don't have the time nor the motivation to double-check details of my project team's work.

And it's really embarassing (in a trust-based relationship-business like consulting) if you base your recommendation and take-aways on wrong data, and it's even more embarassing if it would have been logically correct but just unnecessary carelessness about the numbers led to that situation.

You might get away with that once, maybe twice. Third time one of us will leave the organization, and I believe it's not me ;-)

Take-away: not only double-check, even triple-check your numbers - especially if you know already you are prone to such mistakes (and even if it's already 3am after a long day), and always do a sanity check to see if the numbers somehow are in a range of what you reasonably expected.

And make sure you never ever get a connotation about being sloppy with numbers - nobody will want to have you on his team.

Hope this helps - if so, please be so kind and give it a thumbs-up with the green upvote button below!

Robert

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Francesco
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replied on Jun 08, 2020
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Hi there,

the only way to assess if a number is correct is to do a double-check it. You can do this in two ways:

  • Reviewing your numbers/computation. Go back to the formula and perform computations again.
  • Comparing your results with something else based on business acumen. If you get that the revenues of Microsoft are $800B, and you know the top F500 is doing $500B, you know there is a mistake somewhere.

The more you develop experience, the more the second method becomes natural.

Hope this helps,

Francesco

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Emily
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replied on Jun 08, 2020
BCG Project Leader | 3+ years interview experience for BCG SEA recruiting | Kellogg MBA, NTU, Peking University

Hi there,

Whenever you get to a numerical answer, remind yourself to sense check the number.

  • Does it make sense in the context?
  • Does it look like it is in the right magnitude?
  • How does it compare to the historical numbers, or how does it compare to a benchmark/reference?
  • Is there anything odd, and if so, do you have a good reason or is there a mistake?

Force yourself to ask these questions each time and form a habit of sense checking on numbers. Then you'd be able to spot error (if there is one) before your interviewer/manager.

Hope it helps,

Emily

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Clara
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replied on Jun 08, 2020
McKinsey | Awarded professor at Master in Management @ IE | MBA at MIT |+180 students coached | Integrated FIT Guide aut

Hello!

This is super common, what we call in Spanish having the "big numbers"

Two advises:

  1. Have ratios in your head at all times, so you see the order of magnitude of numbers in each step
  2. Problem solve with the interviewer a lot by challenging your own answers (e.g., would 5M make sense, do we have any benchmark data to proof this?)

Hope it helps!

Cheers,

Clara

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Anrian
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replied on Jun 07, 2020
Kearney Senior Manager | Ex McKinsey Engagement Manager | Interviewer & Case Coach at McKinsey (200+ Real Interviews)

Hi There,

Are you referring to case interviews or daily work use?

If it's for daily work use, I suggest to ALWAYS double-check or even triple-check your calculation in the Deck or Excel, make this as your habit. I had the same feedback (calculate very quickly, but easy to make mistake) in my first year at McKinsey. It was hard for me to develop this habit at first, but the job required me to be like that - and it carries until now.

As for the case interview, you have to make sure you are clear with all the information and the objective - ask clarification as much as you want before jumping into the calculation. And when you start calculating and get the result, double-check again before communicating it to the interviewer. An ideal situation is if you are able to do the calculation while saying it out loud, so in case you make a mistake during the calculation - the interviewer can intervene. Lastly, make that as your habit.

Hope that helps!

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Anonymous replied on Jun 07, 2020

Hello,

Rigor with numbers is indeed something to which managers are very sensitive. You must systematically:

  • Make sure the numbers make sense (take a little height on the values ​​you determine)
  • Check that the figures are consistent from one slide to another
  • Ask yourself if your analyzes are self-explanatory or if it would be necessary to make an additional analysis so that everything is clear

Finally, clearly ask your manager if he has specific examples that will help define the right action plan. Do not hesitate to come in PM if you want to discuss it in more detail.

David

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Anonymous replied on Jun 07, 2020

Hi there,

What I usually do after putting in numbers of a PPT of Excel document, it run ratios in my head - (does X over Y make sense? does X divided over N years make sense?)

This is what partners do when they review the results of a business model scenario - they create ratios in their heads and see if the output of the scenario makes business sense - this is how you catch a mistake on a slide/excel and this is how to start seeing the numbers make sense or not.

Plus this technique will leverage your strong quantitative skills ;)

I hope this helps

Khaled

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Anonymous replied on Jun 09, 2020

Dear A,

One more tip to add to what experts said, if the sums are correct this probably means in 90% that also all further members are correct.

I hope that the business sensitivity will come to you over the time.

Good luck,

André

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Axel
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replied on Jun 09, 2020
Bain Consultant | Interviewer for 3 years at Bain |Passionate about coaching |I will make you a case interview Rockstar

My recommendation to you would be to start using some methods to always sense check your numbers when you are finished calculating. You need to develop habits that automatically kick in and will allow you to capture these errors before they are presented to the interviewer or added to a final presentation/document.

- Is the number the right magnitude?

- Is it the right units?

- If I round up down to an easier to calculate number is the results roughly the same?

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Ian
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replied on Jun 09, 2020
BCG | 100% personal interview success rate (8/8) and 95% candidate success rate | Personalized interview prep

Hi there,

I highly recommend you use the following to practice your fast math:

  • Online "Drills": https://www.jetpunk.com/quizzes/fast-math-multiplication-quiz
  • Math sheets (print these and do them on paper): https://www.math-drills.com/
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Robert gave the best answer

Robert

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