W3C home > Mailing lists > Public > w3c-wai-gl@w3.org > April to June 2004

RE: General Usability DetecVS tor

From: Gregg Vanderheiden <gv@trace.wisc.edu>
Date: Mon, 10 May 2004 09:56:56 -0500
To: <w3c-wai-gl@w3.org>
Message-ID: <auto-000031960302@spamarrest.com>


   I don't know where the implication that the times needed to be in round
numbers or that the numbers weren't derived from user testing came from -
but that was not my intention.    I was talking about results from user


Also - this was not meant to be a 'final determination' but rather a sniff
test.    If something slows people with disabilities down the same
proportionate amount as people without disabilities - then I look at it more
carefully to see if it is indeed just a usability problem rather than an
accessibility problem.


Here I am defining accessibility problems as problems that result from a
person having a disability and that affect them in ways or in proportions
that are not experienced by everyone else (without that disability). 


Again - please note that this is NOT something that I am proposing as a
definition or for use by our group.  It was simply something I found useful
when looking at problems in this area - and I posted to the list because
others found it an interesting idea to roll around in their heads.  




 -- ------------------------------ 
Gregg C Vanderheiden Ph.D. 
Professor - Ind. Engr. & BioMed Engr.
Director - Trace R & D Center 
University of Wisconsin-Madison 


From: w3c-wai-gl-request@w3.org [mailto:w3c-wai-gl-request@w3.org] On Behalf
Of Gordon Montgomery
Sent: Monday, May 10, 2004 7:17 AM
To: w3c-wai-gl@w3.org
Subject: Re: General Usability DetecVS tor


Time cannot be used as a reliable indicator of usability.


Firstly you will not get "times" that are nicely differentiated like 2mins
vs 4mins


It will be more like 2.1 mins vs 2.25 mins.


Then there's the issues of when the task started, the level of verbosity of
the participant

and level of success related to the completion of the task.


Finally, satisfaction plays a big part too. Just because a task takes a few
extra seconds may not mean

that participants are any less satisfied with the effectiveness [their
success] or efficiency [their effort] of the interface.

In fact those few extra seconds may indeed add to satisfaction in some cases
and leave the participant

feeling that the interface is more usable.



So to answer your question you cannot differentiate [nor should you]
accessibility and usability issues a priori.

The only way to know if issues are particular to the disabled is to test
with those intended users.

That involves running a formal usability test.


Accessibility has a lot to do with the coding we use for web pages etc and
that sadly is where it has

always lost traction with the wider commercial world. Until we make testing
with real users the central theme then

accessibility will continue to reside in an esoteric, "not my problem"
backwater as far as most corporations

are concerned.





"Are you still wasting your time with spam?...
There is a solution!"


Protected by GIANT Company's Spam Inspector
The most powerful anti-spam software available.



----- Original Message ----- 

From: Gregg Vanderheiden <mailto:gv@trace.wisc.edu>  

To: w3c-wai-gl@w3.org 

Sent: Monday, May 10, 2004 12:46 AM

Subject: General Usability DetecVS tor


In discussions on our last call "usability" came up since it was a question
from one of our reviewers


How do we separate

"Accessibility / Usability problems that are specific to disabilities" 


"usability issues that are faced by all users"



One test I have sometimes found useful in examining this question is 

   "Does it multiply the time and effort for people with disabilities by the
same amount as people without disabilities?"

If the multiplier is the same - then it may be a general usability issue.


For example

Good page    2 min  for  no disability

Good page    4 min for screen reader user


Bad page      3 min for no disability

Bad page       6 min for screen reader user


This bad page appears to be 50% harder for both groups.   This looks more
like a general usability problem rather than accessibility since it slows
everyone down by the same factor



Another example


Good page   2 min for no disability 

Good page   4 min with screen reader


Page 2  -    3 min for no disability

Page 2  -    10 min   with screen reader. 


Page 3  -    3 min for no disability

Page 3  -     cannot get at some of the information with screen reader. 


These look like accessibility problems 

Page 2 is much more than proportionately harder (250% vs 50%)

Page 3 is inaccessible 



Just passing along in case it is of use to others in thinking about the





Gregg C Vanderheiden Ph.D. 
Professor - Depts of Ind. Engr. & BioMed Engr.
Director - Trace R & D Center 
University of Wisconsin-Madison 
< <http://trace.wisc.edu/> http://trace.wisc.edu/> FAX 608/262-8848  
For a list of our list discussions http://trace.wisc.edu/lists/



Received on Monday, 10 May 2004 11:02:11 UTC

This archive was generated by hypermail 2.3.1 : Tuesday, 16 January 2018 15:33:49 UTC