The power of "stochastic thinking"

Why was the wearing of face masks by doctors in the USA not encouraged? Every doctor interviewed by the media said they were not that effective. How can they not be effective? Even if they reduced transmission of droplets by 30% that would be effective in reducing overall R0, and therefore growth in the [logistic function]( So why were they not recommended? Could it be the doctors realized people would start hoarding surgical masks in an emergency, thus reducing the amount available at hospitals?

Why not tell people how to make their own mask? Even if was only 20% effective instead of 30% effective it would be good. Maybe this isn't done because western people don't understand stochastic thinking, but perhaps the people of the far east do?


From 2009 :

How to make an anti-infection mask easily from paper towel

Swine flu is spreading all over the world and the number of patients is growing every each day.

Maybe it's not familiar to those who are out of Japan, but in Japan, when you got cold, it's very common to wear a mask covering mouth and nose. The flu mainly passes on by droplet transmission caused by coughs and sneezes. So the mask may not cover you from virus but will help preventing further infection from you to others.

Here's the step-by-step instruction of how to make a transmission preventing mask from paper towel, written by a doctor of Katakai Hospital in Niigata pref.

(JP)Making masks from Paper Towel

What you need is a sheet    
of paper towel, 2 rubber   
bands, & a stapler.   

Fold a paper towel in two.   
You may want to pile up 2   
or 3 towels in one.  

Fold to the center.

Fold the shown part
in half


Flip it back and
fold to center


Fold at center and make
an accordion-like thing


Place rubber bands on
both sides and fix them
with stapler




Change the position of rubber
bands to adjust the size.


We should warn you that it will not be a perfect defense for viruses. But you need a mask in hurry, this tip will do.