OU blog

Personal Blogs

Dr Who?

Two Spies and a Paradox

Visible to anyone in the world
Edited by Richard Walker, Wednesday, 20 Jan 2016, 01:31

Once upon a time there were two spies, code-named M and N, who worked for rival departments.

By coincidence on one particular day M and N were both assigned to 24-hour surveillance of the email messages sent by a dastardly counterspy X to one of her accomplices Y.

The messages were cunningly encrypted, so the content was unreadable, but it was hoped that monitoring the number of communication would indicate whether or not a crisis was looming and action would need to be taken.

A downward trend during the day would indicate there was no cause for alarm; conversely an upward trend would indicate danger.

M counted the messages sent in each 12-hour period and submitted a report with a graph showing a clear downward trend.


N counted the messages sent in each 8-hour period and submitted a report with a graph showing a clear upward trend.


Yet the equipment used by each spy was perfectly reliable, and they recorded the data accurately. How can this paradox be explained?

Permalink 3 comments (latest comment by Cathy Lewis, Thursday, 21 Jan 2016, 08:16)
Share post

This blog might contain posts that are only visible to logged-in users, or where only logged-in users can comment. If you have an account on the system, please log in for full access.

Total visits to this blog: 1015147