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2 or 3 levels: beware of the compromise effect

From: Yvette P. Hoitink <y.p.hoitink@heritas.nl>
Date: Fri, 26 Mar 2004 00:21:55 +0100
To: <w3c-wai-gl@w3.org>
Message-Id: <20040325232139.20A65A1BE4@frink.w3.org>

Hello everyone,

Tonight we talked about whether we should have 3 or 2 levels of conformance.
I remembered a case study from when I was taking management studies classes
and looked it up again (thanks Google!). This study showed that people did
not want to choose the extreme option and were more likely to choose the
second option if they could choose between 3 instead of 2 options. McDonalds
has known this for quite a while: letting you choose between small, medium
and large means more people will choose medium than without the large
option. In literature, this is known as the 'compromise effect'.

This article explains this phenomenon in clear terms:
http://www.indicator.co.uk/books/uk101sbk/example1.htm. A more scientific
explanation can be found here:
http://www.anderson.ucla.edu/acad_unit/marketing/seminar_papers/Srinivasan.p
df.

In WCAG terms, the compromise effect means that more people will be aiming
for level 2 if they can choose between 3 levels than if they could only
choose between 2 levels. Thus, from a psychological point of view I would
argue against 2 levels instead of 3.

Yvette Hoitink
Heritas, Enschede, the Netherlands 
Received on Thursday, 25 March 2004 18:21:39 UTC

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