I had a market sizing question just yesterday, lasted more than 30 mins: Accenture round 1, had to estimate the market size of smart homes in the UAE.
I had a straightforward logical standard approach, validated by the interviewer.
As I tried to fit numbers to the different buckets, I was guided by the interviewer and asked to provide more detail where he saw fit.
He eventually led me to doing a market sizing within a market sizing! He did not want me to estimate the average household occupancy, he wanted me to estimate the number of housing units in the UAE and then divide the population by the number of units to get the average number of people per unit. To make it tougher, I had to segment everything by expats and locals.
The trick here was to remain calm.
So my tips to you are:
- remain calm, do not let the element of surprise take over,
- do not stress out (when you stress blood goes to your limbs instead of your brain, very unproductive),
- take a minute to think and back up your numbers with logical arguments,
- do not just blurt out the first thing that comes to mind,
- label your data and get the maths right,
- sense check your answers.
Best of luck!