[LINK] Cheap, popular and it works: Ireland's contact-tracing app success

[Roger Clarke]

On 21/7/20 12:16 pm, Glen Turner wrote:
> I'd add that success should be measured by the system's usefulness to
> contact tracers.
> 
> Conversely, the Apple+Google model places the person holding the phone
> as the "user" of the app. I'd argue that this is a US-centric view not
> well suited to countries with effective public health agencies.
> 
> BTW, I'm not sure that accuracy is an attribute needed for success.
> Consider that requiring the scanning of a big QR poster upon entry to a
> commercial premises isn't that accurate but would be just as as
> effective for contact tracing as all the Bluetooth messing about.

The 'accuracy' thing has been critical to the success of manual
contact-tracing.  They haven't extended the catchment too far, and
consequently they have cred, and people who they nominate as being
at-risk generally take them seriously.

A major problem with Bluetooth signal-strength as a proxy for proximity
is that the correlation between the two can be petty poor.  So, to
include enough really-at-risk people in your list, you have to open out
to include a lot of low-risk people as well.  (Leave aside the 6-12
other problems with the whole 'put your trust in tech' approach).

The QR-code-at-the-shop-entrance has similar problems, because it too is
a poor proxy for proximity.  It may have some application in a very
small shop (extreme case: premises in which most people go to the
counter and it's the shop-assistant who was the carrier), but even then
the time factor can matter.

We should be drawing on the distilled wisdom of the contact-tracing
teams, to work out the factors that they consider - and to find out the
contexts in which they fear they may have missed some people who, with
hindsight, they should have prioritised for isolation and testing.


-- 
Roger Clarke                            mailto:Roger.Clarke at xamax.com.au
T: +61 2 6288 6916   http://www.xamax.com.au  http://www.rogerclarke.com

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Visiting Professor in the Faculty of Law            University of N.S.W.
Visiting Professor in Computer Science    Australian National University