I recently had an interview where I was asked How many mobile phones do you think are in use in London? I really struggled with this and wondered if anyone had any advice on how to answer questions like this so I can improve next time.
We did a webinar on these type of question last month, and went through this but across the UK rather than London.
There isn't a right or wrong answer to this. They are just trying to see if you can factor in variables and come to some form of logical conclusion.
When we did the seminar we factored in:
- Population size
- Age of population
- How many people may have multiple phones
- Whether non-working phones are included, or are we just talking about phones connected to a network (not the old devices you have stored in cupboards/draws)
We then did very rough calculations to make it easier.
Eg rounded 67 million to 70.
Divided age ranges into 10 (0-10, 11-20…. 91-100)
We then removed the bottom and top age ranges as unlikely to have phones
We estimated 10% of the remaining age groups might not have a mobile phone
We estimated 80% of those with a mobile phone either have an active second phone (eg for work) or due to device upgrades etc
We got to a figure of 90 million based on this. When we looked it up it was 81 million (based on active subscriptions) so we didn’t feel this is way off.
With these answers it is more about explaining the assumptions you are making and what you are factoring in/what you aren’t, and coming to some fairly quick conclusion on it, rather than fundamentally being right or wrong.