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Re: Another comment about confidence value.

From: Karl Dubost <karl@w3.org>
Date: Tue, 19 Apr 2005 13:47:32 -0400
Message-Id: <c77edac310619cefc8aaf47be44dcbff@w3.org>
To: public-wai-ert@w3.org
Hi,

Le 18 avr. 2005,  10:33, Giorgio Brajnik a crit :
> I would suggest to consider confidence factors as probabilities 
> associated to assertions (like "this test has failed").

I hope I have understood the main points of the discussion. I'm still 
not sure yet. We have argued in QA against percentages for 
*conformance*. We don't want that someone says for a technology. We 
implemented 75% of the technology, because it doesn't make sense in a 
conformance model and it doesn't mean anything about interoperability.

I understand the notion of level of confidence for a measure, but I 
want to be sure we do not mix anything.

In scientific studies, a measure is always associated with an error 
(calculated or estimated with different techniques). The collection of 
x times the same measure helps to define, refine a level of confidence 
for the results.

T being the temperature, Sundays in April 2005 at noon from an 
imaginary location.

T(2005-04-03) = 20.0C +/- 0.3C
T(2005-04-10) = 22.3C +/- 0.2C
T(2005-04-17) = 23.4C +/- 0.4C

Each result is unique. The level of confidence is calculated when a  
large collection of Sunday's temperatures has been acquired.

What is the temperature at noon on Sunday?

In an equatorial climate, the level of confidence will be good. In a 
temperate climate, it will be very poor.

I see EARL giving the possibility to report the first series of 
measures. The report for the level of confidence is then another level 
of test and calculation somehow disconnected from the first series. So 
I'm not sure the level of confidence is really part or EARL or more an 
artefact of measurement.

How will we express it in EARL?

Am I off-track here?


-- 
Karl Dubost - http://www.w3.org/People/karl/
W3C Conformance Manager
*** Be Strict To Be Cool ***

Received on Tuesday, 19 April 2005 19:21:13 GMT

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