Piano Tuners and Pre-op assessment

Posted By Paul Cooper |  last update 10-Mar 2011

"how many piano tuners are there in Chicago". No other information given.

I was first posed this problem at school in the 1970s , and expected to come up with an answer. (125, as you ask)

Its an example of a Fermi problem. Make some reasonable assumptions, and see what you get. if you make  enough assumptions and there is no systematic bias then you should get a 'reasonable' answer and the overassumptions and under-assumptions should cancel each other  out .


q how many pre-assessment nurses are there in the UK ?

1. There are 3 million procedures performed /yr  in the UK, and the vast majority  will have a preoperative assement  of some sort.
All the pre-op assessment clinics i know of are staffed by nurses .

So 3 million procedures = 3 million assessments by nurses

2. An appointment  + associated paperwork will on average  be 40 mins.
So in a working day a nurse will see  9 patients   ( = 6 hours + hour for lunch + hour for other sundry tasks).
In a working week this is 9 x 5 = 45 patients.

3. A nurse will work for 45 weeks /yr , so in a year 1 nurse will see 45 x 45 patients = approx 2000 pts

so 3 Million / 2000 = 1500  nurses nationally .

And there are 168 Acute Trusts in the UK ( as of 2009)

so this means  1500 / 168 = 8.9 nurses / Trust

To check this Ive just rung up our preop assessment unit for my medium-sized Trust and asked how many WTE nurses we have.

We have 6.

Who needs expensive, time -consuming national surveys then ? 

2 comment(s)

Posted by paul cooper on 13-Mar 2011 15:03

more Fermi problems :

How much landfill is occupied by TIVA syringes ?

How much paper /yr does your department use? 


Posted by apmadden on 13-Mar 2011 15:03

Excellent! Obviously we don't need a census. There's some fascinating stuff on the interweb about the Fermi problem/question/estimate, like how he estimated the strength of a nuclear bomb test. There's also a decent amount of academic stuff for those who would like to know more. And don't forget the Drake equation, which many think is complete nonsense (multiply several probabilities together, each with a value between 0 and 1, and the answer will be somewhere between 0 and 1!).

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