Re: Hidden information question

Schizoid Man wrote:

Several coworkers would like to know their average salary. How can they calculate it, without disclosing their own salaries?

Get piece of paper.
First person picks a random number (+ or -) known only to him/her and adds it to his/her salary. Writes only the total on piece of paper.
Paper goes around the room with everyone else adding his/her salary to the total.
When it comes back to the first person s/he subtracts the random number.

(This has to be done in such a way that no one can follow the running total. Perhaps everyone has a piece of paper. S/he keeps the one that comes to him/her, passing on a *** with only one number: the sum of the number that came to him/her plus his/her salary.)

How does one calculate the mean for a set of random variables, if one does not know:
1. the value of the variables, or
2. the parameters (i.e. mean, std dev) of the distribution?
.