Re: 48px vs 44px target sizing

I agree we have to look carefully... we want to have a WCAG 2.1 that makes
sense to all, otherwise WCAG 2.1 will end up like the sequels to the
"Matrix"... flat and not accepted by our stakeholders.

I've read through the reference sent by John looking for things that might
help us... there are also several useful references that we may want to
look up. There are 4 pages missing from the 16 page report in the Google
book version but I think I can pull the major parts of it. Here are some
quotes and a summary of key findings pertinent to our work.

"When creating the prototype, we referred to research on appropriate button
size [ 14, 15], button spacing [ 15, 16], and touchscreen gestures and
button position [11, 17]. In our mobile voting user interface design,
buttons arc located near the edges of the screen and the active region of
each button is at least 20 mm in length and width (although the visual size
may appear smaller), with at least 6.35 mm of spacing between active
regions. Where buttons arc touching, the minimum button size was increased
to provide additional spacing. All functionality is accessed via tap, which
is the preferred and most effective gesture for individuals with motor
skill impairments [ 11 ]"

"although the amount of spacing included between these buttons and the
placement of the buttons along the edges of the screen was based on
previous research, we observed that his spacing proved insufficient,
especially for w participants who tended to experience drifting. This
proximity of repeated-press buttons led to accidental presses of the Next
Contest button ... "


​Here's a summary of other points.

   - Buttons in study were were 20mm = 75px with spacing of   6.35mm = 24
   px  (conversion here https://css-tricks.com/the-lengths-of-css/ ) This
   was based on research listed below.
   - Users did better with mobile device on slanted table​
   - Resting hand alongside of the device for support helps some users
   - buttons on edge were better because user could support arm
   - left and right hand versions of software are helpful for this reason
   - 4 out of 16 participants did not have success when they touched the
   Samsung Galaxy Tab4, probably because of excessive dwell times were
   recognized as double press rather than single.
   - some users used their thumbs and fingers other than the index finger
   - Button placement personalization would be helpful.
   - People with dexterity problems required twice the time. (literally)
   - Accuracy of control group wass 88.8% vs 65.3% for users with dexterity
   problems. 4 users w/ disabilities failed the task with less than 70%.
   - much of their findings is consistent with previous literature.


References #11, 14, 15, 16​, 17 are as follows:

11, and 14 are on pages left out of the Google book.

15. Touch screen user interfaces for older adults: button size and spacing
(Jin, Z.X, Plocher, T. Kiff, L., HCI 2007 LNCS Vol 4554. pp. 933-941,
Springer, Heidelberg 2007
16.  Effect of touch screen button size and spacing on touch
characteristics of users with and without disabilities. Human Factors
Ergonomics Soc. 54(3), 425-436 (2012), Sesto, M.E. Irwin, C.B., CHen, K.B,
Chourasia, A. O, Weigmann. DA

17.  Mobile touchscreen user interfaces: Bridging the gap between
motor-impaired and able bodied users. Univ. Access Inf. Soc. 13, 303-313
(2014)


Here's the research paper John referred to summarized here.

https://books.google.com/books?id=9hOfDAAAQBAJ&pg=PA159&lpg=PA159&dq=
Touchscreen+voting+interface+design+for+persons+with+
disabilities:+Insights+from+usability+evaluation+of+mobile+voting+prototype&
source=bl&ots=2a0DJQeVh6&sig=vnbIDBLP6OQcTO-EJIp9L30eM2c&hl=en&sa=X&ved=
0ahUKEwjruJqjudvOAhVDtRQKHb-bCGoQ6AEIMjAE#v=onepage&q=Touchscreen%20voting%
20interface%20design%20for%20persons%20with%20disabilities%3A%20Insights%
20from%20usability%20evaluation%20of%20mobile%20voting%20prototype&f=false









Cheers,
David MacDonald



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On Mon, Sep 5, 2016 at 9:00 AM, Alastair Campbell <acampbell@nomensa.com>
wrote:

> David wrote:
> > “We've seen studies recommending up to 57px... We went back and forth on
> 50 px but dropped it to 48px for the very reason you mention regarding
> Android devs...  Are you recommending further reduction?
> > It would make sense for an accessibility standard to take the upper
> limit not the lower....”
>
> Ideally there would be a well-researched, known minimum size that easily
> translates into CSS pixels, and the platform standards would all use that.
>
> However, we aren’t there so I think it would help to have a common
> ‘story’, either:
>
> - It uses the lower end of the platform standards and we can say “use
> platform standards”.
>
> OR
>
> - It uses something larger than any of the platform standards, so we can
> say “The platform standards aren’t enough, please make targets bigger”.
>
> Choosing the upper end of the platform standards is messy, it means that
> some developers don’t have to worry, others do.
>
> So there are three options compared to the platform standards: 1) lower
> end; 2) upper end; 3) above.
>
> In the case of 2 or 3, there needs to be a good rational for why the
> platform standard (i.e. iOS) is not large enough.
>
> Sorry that I have probably missed that reasoning, but this is the type of
> push-back that Alan was talking about so I’m just trying to preempt it!
>
> Cheers,
>
> -Alastair
>
>
>